Publishable JRP Summary for Project T4 J02 (NanoSpin).
Nanomagnetism and Spintronics
Aim:
The goal of NanoSpin is to establish a sound metrological basis for the field of nanomagnetism. The project is designed to deliver measurement methods and reference samples for industrial stakeholders and scientific partners.
Main achievements and implications:
In the field of nanomagnetism and spintronics, exciting new developments are under way in applications ranging from ultra strong magnets, spin polarized materials, ultra high density recording media (hard disks, flash memories/MRAM), spin transistors, spin-based qubits, leading to potential mass market products such as the instant boot computer, computer in a test tube and ubiquitous DNA- and bio-sensors. All these developments and potential mass markets urgently require measurement tools to reliably characterize magnetic nanomaterials and structures with verified traceability to existing standards: to date there are very few producers of magnetic nanostructures and nanomaterials who are able to provide them. Such traceability is also indispensable for a sound risk assessment of nanomaterials e.g. in the health sector. The value of the project NanoSpin is thus associated to the development of magnetic measurement techniques and materials at the frontier of current technical capabilities, which are under fast development and industrial exploitation in Europe and worldwide. It is expected that the project NanoSpin will be able provide reference samples, measurement methods and services to industry and academia.
The work has been subdivided among different workpackages (WP)
The WP Reference Nanomaterials is associated to the production and patterning of reference nanostructures. Nanopatterned and self-assembled soft and hard magnetic reference materials are designed and fabricated. Characterized reference materials will be made available to laboratories and industry to disseminate and exploit the results of this JRP. Reference materials are directly involved in the traceability chains and are essential since they allow for the comparison of measurements and for the validation of the results through sample exchange. Therefore the WP reference materials is a fundamental part of the JRP.
Results achieved from June 08-Oct 08
· A first set of FeBSi and Permalloy thin films has been produced, characterized at INRIM and distributed to PTB (see WP3)
· A coplanar wave guide has been designed by PTB for inductive detection (see WP3)
· Lithography tests are under way both at PTB and INRIM for further activities in the integration of materials and circuits
· A first sample of FePt has been produced and heat treated by IMEM Parma for INRIM. The sample has been transferred to PTB for further processing and patterning.
· A Co target will be used with Cr chips for film production at INRIM. Materials are under machining into final geometry for sputtering.
· Contacts are under way with Politecnico di Milano and Hitachi Research Center for obtaining additional perpendicular anisotropy film samples
· Size monodispersed Fe oxide magnetic nanoparticles (12 nm) have been produced and characterized at INRIM
Results achieved from Nov 08-Apr 09
· Production and distribution of NiFe thin films of different thickness and geometry
· Clean room fabrication of coplanar wave guides for inductive detection of magnetization dynamics of unpatterned thin films. Mask design of coplanar wave guides for reference samples with integrated patterned magnetic thin films.
Results achieved from May 09-Oct 09
· Production and distribution of NiFe thin films of different thickness and geometry
· Clean room fabrication of coplanar wave guides for inductive detection of magnetization dynamics of unpatterned thin films. Functional waveguides are now available with integrated materials. Tests are under way
· Hard magnetic films have been patterned with different feature sizes. Control tests are under way. A new partner has been identified for had magnetic thin film production.
· Several types of nanostructures were produced or obtained from scientific partners and characterized by magnetometry, among those:Nanoparticles; Nanowires and coaxial nanocables ;Thin films and multilayers. In all cases the magnetization of the sample was studied as a function of the magnetic field and temperature. Effects of thermal and magnetic history were investigated.
Results achieved from Nov 09 - Apr 10
· Production and distribution of NiFe thin films of different thickness and geometry
· Clean room fabrication of soft magnetic reference samples with integrated patterned magnetic thin films. Variation of sample geometry (position, width and length of magnetic pattern, and of coplanar wave guide).
· Fabrication of MTJ pillars for spin torque dynamics measurements.
· MBE growth of first GaMnAs ferromagnetic semiconductor thin films.
· Hard magnetic CoPt films for the production of reference samples were obtained from external TU Chemintz. Several experiments showed that the patterning of hard magnetic films into reference structures with FIB causes a degradation of their magnetic properties.
· Alternate patterning process was employed using a photoresist mask and ion beam etching. The new samples appear to be more stable but improvements are necessary.
The WP Time and frequency domain dynamics is designed to achieve traceable inductive and magneto transport measurements in the time (50 ps resolution) and frequency domain (20 GHz frequency) including full uncertainty budgets. Standard procedures for the characterization of different types of materials and devices will be derived from a comparison of the different measurement techniques and disseminated to industry and the scientific community. To facilitate comparisons, reference samples will be used that are designed and fabricated during the project. These samples also allow for the validation of measurements: validated traceable inductive measurements of ferromagnetic resonance and damping of soft magnetic thin films on reference samples (up to 20 GHz); magneto transport metrology of spin transfer torque dynamics of magnetic nanodevices (up to 20 GHz); inductive metrology at temperatures down to 1.5 K for precessional dynamics of diluted magnetic semiconductors
Results achieved June 08-Oct 08
· Measurements setups at the participating institutions have been up adjusted for the Project goals
· Time domain and frequency domain measurements and data analysis leading to the determination of the damping parameter alpha on an FeBSi sample were made.
· Magneto transport experimental setups for tests on individual nanopatterned spin valves and magnetic tunnel junctions are under development at PTB and INRIM.
Results achieved from Nov 08-Apr 09
· Time domain inductive characterization of FeBSi and NiFe (Permalloy) reference thin films from INRIM.
· Data analysis of and fFMR of frequency domain data of FeBSi reference thin films as function of applied magnetic field.
· Magneto transport experiment for measurement of spin torque dynamics of individual magnetic tunnelling junction nanopillars installed.
· Vector magnet cryostat system for measurements of magnetization dynamics of diluted ferromagnetic semiconductors has been ordered. Planning of system installation has been performed.
· Characterization of static magnetic parameters of NiFe (Permalloy) reference thin films sputter deposited at INRIM.
· Frequency domain inductive characterization of FeBSi and NiFe (Permalloy) reference thin films from INRIM.
· Data analysis of alpha and fFMR of frequency domain data of FeBSi and NiFe reference thin films as function of applied magnetic field.
· Comparison measurements of frequency domain data obtained on two different wave guide geometries.
Results achieved from May 09-Nov 09
· Comparison measurements of frequency domain data obtained on different wave guide geometries was performed in the frequency domain in collaboration with Tohoku University
· Issues in repeatability of alpha measurements were identified in the sample conditions and sensitivity to ambient conditions which were removed by proper sample conditioning.
· Time domain tests are under way on integrated samples using patterned thin films. Functional waveguides are now available with integrated materials in different geometries.
Results achieved from Nov 09 - Apr 10
· Time domain inductive characterization of three sets of integrated NiFe (Permalloy) reference samples.
· Data analysis of a and fFMR of frequency domain data. Ongoing analysis of influence of geometry and circuit on α.
· Positive comparison of data obtained at INRIM and Tohoku University. Additional tests of samples produced at Tohoku University.
· Frequency domain inductive characterization of one set of integrated NiFe (Permalloy) reference samples. Different experimental techniques were used.
· First positive comparison of time and frequency domain results
· Time resolved spin torque dynamics measurements of individual magnetic tunnelling junction nanopillars
· Magneto transport measurements in frequency domain of point contact oscillators
· Magnetotransport tests on planar Co antidots arrays –MR signals detected
· Vector magnet cryostat system for measurements of magnetization dynamics of diluted ferromagnetic semiconductors installed and tested.
· First successful inductive test measurements on CoFeB in frequency domain at low temperatures down to 10K
The WP High Resolution Scanning Probe Microscopy will be devoted to the development and technological dissemination of a quantitative and traceable MFM imaging technique of magnetic fields and magnetization distributions on the 50 nm scale using a transfer function approach to calibrate MFM tips. To achieve this challenging goal a traceability chain will be established using magneto optics, Hall sensors, and specific hard magnetic reference samples with calculable stray fields. Demonstration of stray field imaging by scanning Hall microscopy with resolution < 1 m will be sought. In parallel a scanning probe microscope capable of low-temperature (down to 4 K) and high-vacuum operation based on a tuning fork sensor will be developed.
Results achieved June 08-Oct 08
· For the design of reference samples a software algorithm was developed that optimizes arbitrary real space structures with respect to their Fourier spectrum. The optimized structures will be used to produce reference structures by patterning hard magnetic films.
· An indicator film with suitable characteristics has been obtained for magnetooptical measurements on patterned reference samples with sub micrometer structures.
· Design options were investigated for Hall probes dimension and probe-sample distance.
· Operation modes of the tuning fork SPM and techniques for the attachment of sensors to the tuning fork have been established. Scanning probe imaging has been demonstrated.
Results achieved from Nov 08-Apr 09
· A first reference sample has been designed and a hard magnetic FePt film (10.7 nm thick, L1 0 ordered phase) was obtained from an external supplier. The patterning was done at NPL.
· The stray fields of the structures were characterized with magnetic force microscopy at PTB.
· A software has been developed that allows for an automated analysis of MFM images. It will be used for the implementation of the tip calibration procedure.
· Progress concerning the development of nanopatterned Hall sensors.
· Several samples of magnetooptic indicator films prepared by an external manufacturer were tested at UME. The highest saturation field was found to be around 3 kG (6 kG are required for magneto optic observations on reference hard magnetic samples
· Tuning fork sensors were equipped with Pt or Co-coated tips using the previously developed glue-less tip attachment technique.
· Topographic images of semiconductor Hall bars have been obtained. Operation in vacuum rather than in air resulted in drastically faster feedback and sharper images; Operation at 77 K achieved significantly smaller hysteresis and non-linearity in XY.
· Multichannel data acquisition has been achieved.
· Transverse voltage of a current-biased Hall bar was recorded simultaneously with imaging at room temperature in air using a Pt-coated non-magnetic tip.
· A reference FePt sample for a quantitative MFM was fabricated by FIB patterning (array sizes 50x50, 20x20, 10x10 and 2x2 um2 ).
· Initial AFM/MFM analysis of the sample was performed. Good magnetic contrasts were obtained from the arrays with sizes of 50x50, 20x20, 10x10 um2
Results achieved from May 09-Nov 09
· Complete AFM/MFM analysis of the samples were performed. Good magnetic contrasts were obtained from the arrays with sizes of 50x50, 20x20, 10x10 um2
· Images of high quality were obtained on the larger patterns where very sharp features were observed with good MFM contrasts.
· Several hard magnetic film systems were tested, and additional sample processing procedures to enhance results are under test
· an automated procedure for the evaluation of the MFM data has been developed which includes noise filters, edge detection algorithms and an FFT software. It will be used for the implementation of the tip calibration procedure
· several samples of magnetooptic indicator films have been characterized at UME with a saturation field of 3 kG at most. New films have been developed by an external supplier.
· Hall bars were patterned by optical lithography with dimensions of the order of 100 µm 2. Tests are under way to reduce size.
· A commercial scanning probe microscope has been purchased and installed and tests of the AFM mode are in progress.
· The performance of the tuning fork Scanning Probe Microscope has been improved and tested.
· Tuning fork sensors were equipped with different metal coated tips using the glue-less tip attachment technique.
· Using the above system topographic images of semiconductor Hall bars have been obtained with good imaging obtained in vacuum. Additional imaging improvements were obtained at 77K
· Using the tuning fork with a magnetic tip we investigated the spatial distribution of the Hall sensor sensitivity which allows quantitative 2D mapping of a Hall (or any other magnetic) sensor output with a spatial resolution of 10 nm.
· A 2.3 µm wide InSb Hall bar was first calibrated .Using a tuning fork SPM system a spatial distribution of the sensor response was obtained. The sensitivity map was superimposed with the topographic image. This technique might provide a convenient traceable in-situ calibration route for the magnetised tips, such as those conventionally used in magnetic force microscopy.
Results achieved from Nov 09 - Apr 10
· Testing of calibration software, simulated MFM images of the reference patterns are calculated based on realistic and idealized tip geometries. These images will be used to calculate theoretical tip transfer functions to test the self consistency and the noise tolerance of the calibration software.
· MO indicator films with the desired characteristics have been obtained. They will be characterized using hard magnetic reference samples.
· Sub-microsized Hall sensors were produced and characterized.
· Noise problems in the system of the tuning force MFM had to be solved. In parallel simulations were performed.
The WP on Ultra sensitive magnetic moment detection is directed to the development of a nano-SQUID system with improved sensitivity allowing direct measurements of the magnetic moment of individual magnetic nanoparticles and nanoobjects with a diameter or one dimension down to 10 nm. To this end, a nano-SQUID system which exploits the noise performance of the nano-SQUID front end will be set up. The sensitivity will be pushed below the limit of 102 B/Hz, and potentially below 10 B/Hz. Noise performance will be pushed beyond the present limit of existing nano-SQUID systems of >200 B/Hz. Additionally, industrially relevant ultra small Hall sensors with lateral dimensions below 500 nm allowing room temperature detection of down to 106 µB will be developed.
Results achieved June 08-Oct 08
· Initial modelling and design of a DC nano-SQUID have been performed. It was shown that the optimal flux coupling and, therefore, higher values for spin sensitivity can be obtained for a configuration where the dipole is located directly on top of the nanobridge. Thus, the spin sensitivity of the experiment will be eventually determined by the location of the magnetic particles with respect to the SQUID geometry.
· A new type of Nb nano-SQUID has been prepared using a straightforward bi-layer deposition route, combining photolithography with FIB patterning, producing high performance nanoscale SQUIDs with loop diameter below 300 nm and the constriction size of 65 nm (Fig. 5.1.a). The flexibility of the lithographic and FIB techniques, combined with the advantage of using single-layer Nb films suitably overlaid where necessary by in-situ tungsten films, ensure good reproducibility of the process.
· Initial characterization of Nb nano-SQUIDs has been performed in a variable temperature cryostat with a temperature range between 4.2 and 9 K (Fig. 5.1. c and d).
· Development of SQUID current sensors on the basis of an Nb/AlOx/Nb thin film technology and the read-out electronics necessary for operating the sensors is in process.
· SQUID arrays consisting of 16 SQUIDs in series have been tested. These devices are designed to be used magnetically unshielded in a refrigerator. A highly balanced gradiometric design of the SQUIDs as well as input and transformer coils of the circuit will allow achieving a necessary robustness against external magnetic interferences (Fig. 5.2). Furthermore, the width of the superconducting lines and areas are chosen to be smaller then 3 µm to avoid trapped flux in the superconducting films. The restriction in linewidth makes it necessary to use double transformer stage to match the input coil to the SQUID array. Additional filters and a current limiter in the input circuit accomplish the device. Fig. 5.3. demonstrates the complexity and integrability of the final device.
· On the basis of these SSA current sensors described above, novel sensors have been designed using arrays of up to 32 SQUIDs. These sensors can be operated with so called additional positive feedback (APF) in order to improve the V-f characteristics. Using these improvements, the dynamic range and the bandwidth of the sensors will be enhanced.
Results achieved from Nov 08-Apr 09
· A new mask was designed and a set of Nb nano-bridged SQUIDs has been fabricated. After the construction of a measurement probe for the characterization of nano-SQUIDs in the temperature range T 4 K-9K.
· PTB has built the probe stick and equipped it with all the electronic and cryogenic components which are needed for its operation.
· A superconducting magnetic field coil was implemented to provide relatively large magnetic fields up to several 10 mT which is required for characterizing nanoSQUIDs. These devices have a very low magnetic field sensitivity because of the extremely small loop size.
· During the reporting period, two PTB co-workers have started a secondment at NPL where joint experiments are performed. In these experiments novel NPL nanoSQUIDs are tested together with novel SQUID amplifiers made by PTB.
· Fabrication of large (1300 um x 50 um) Hall bars on various InAlAs/InGaAs commercial heterostructures. 3 wafers with a different interlayer thicknesses are to be tested.
· The way to efficiently remove InGaAs layer down to the InAlAs layer in a controlled and reproducible by chemical etching has been demonstrated.
· Optical lithography has been utilised to pattern a Hall bar (with contacts leads). A first set of 6 Hall bars has been fabricated from each heterostructure, half of them have an additional gate for electron density modulation.
· The experimental setup for Hall sensor measurements has been designed based on metrological requirements, i.e. profile of the magnetic field, its measurement parameters, and thermal stability.
· Two sets of InSb Hall sensors (double-crosses) have been successfully patterned:1st set was fabricated using optical lithography and reactive ion etching. The minimum cross size is 1.5 um. 2nd set of devices was fabricated using e-beam lithography and reactive ion etching. The minimum cross size is 600 nm. All devices in the 1st set have been electrically characterized at room temperature. Noise characteristics and magnetotransport properties of Hall sensors as well as their performance with respect to the lateral dimensions of devices were studied.
· Response of the Hall sensor to an inhomogeneous magnetic field caused by the presence of a magnetic bead was modelled.
Results achieved from Jun – Oct 09
· Design and optimization of the 2nd PTB probe stick and the SQUID amplifiers has been carried out with an improved coil system allowing for two orthogonal field components to the sample holder. The maximum magnetization field is increased up to 100 mT allowing for wider characterization range.
· Deviations of the V-Φ characteristics from the strong periodicity are under study with an electron microscope at 4 K.
· Further development of the measurement system at NPL has been completed.
· The performance of nano-SQUIDs in high magnetic fields was studied.
· At LNE a setup for transport measurements on InAlAs/InGaAs samples was developed in order to probe samples with dc or ac magnetic fields of small magnitude (< 100 G) without significant increase of temperature and allowing precise monitoring of the applied field. Absolute measurements of the Hall resistance are performed automatically
· At NPL a 2nd batch of InSb Hall sensors with the smallest size of to 600x600 nm2 was extensively investigated. The material is characterized by a very good carrier mobility and has excellent dc characteristics
· For detection of a single FePt bead with magnetic moment of ~107 μB a phase–sensitive ac-dc method was used. Although a number of attempts were undertaken previously on detection of small particles, we demonstrate a first nanometer size Hall sensor capable of detection of such small individual magnetic nanoparticle at room temperature.
· Further work on optimization of the contact resistance and, therefore, noise characteristics and magnetic sensitivity is currently underway.
Results achieved from Nov 09 - Apr 10
· A second probe stick for the nano-SQUID characterization was manufactured with an improved coil system intended for the working point adjustment of the nano-SQUID and independent magnetic excitation of an attached nanoparticle.
· The thermal design of the probe stick and chip holders for nano-SQUID and SQUID Series Amplifiers have been improved significantly.
· Parallel experiments are being set up at PTB, NPL and Univ. of Tübingen. These experiments are intended to clarify the observed deviations of the V-Φ characteristics of the nano-SQUIDs from strong periodicity.
· Two new sets of nano-SQUIDs were fabricated and tested at NPL, device with loop diameter of around 350 nm at an operating temperature of 7.8 K, the flux noise referred to the input is white and with very low level.
· In order to position a magnetic nanoparticle at the edge of the SQUID we used a FIB nanomanipulator system. The manipulation procedure involves identifying the single particle in an SEM and depositing near the SQUID. Using this technique three working devices (SQUID-nanoparticle) were prepared. Detection experiments are currently in progress.
· The micro-sized Hall bars have been characterized in the low temperature regime. Three heterostructures have been cooled down to 4 mK within a VTI. The tested samples differ in the doping and the quantum well depth. Density of carriers and the carrier mobility ere determined by van der Paw measurements for all the heterostructures at different temperatures. A very weak variation of the charge carrier density in the temperature range 4 - 293 K ensures a slight temperature coefficient. As a result, a great stability of the Hall coefficient is expected around room temperature.
· Miniaturized Hall cross Heterostructures have been chosen for miniaturization of devices and a first series of nanosensors with various sizes <100 mm and geometries, prepared by e-beam lithography. Lithographic definition of the structures was followed by 3-step device fabrication: Ohmic contacts deposition, RIE mesa etching and interconnection deposition. Some problems with defective contacts. Second batch in preparation.
· A new set of InSb Hall sensors with size of active area down to 600 nm and long gold leads have been patterned. The long leads are designed to minimize the contact resistance and, hence, to decrease the white noise level of the devices.
· New bead manipulation technique was developed. A small FePt bead (diameter ca 140 nm) was positioned on the top of the Hall sensor using a Si membrane.The transport properties and noise characteristics of the Hall sensor remain almost unaffected by nanomanipulation procedure.
· A modeling of 2D sensitivity mapping of the Hall sensor was made. Very good qualitative agreement between simulated and experimental results is demonstrated.
WP Impact
Publications:
· M.Pasquale, E.S. Olivetti, M.Coïsson, P.Rizzi, G.Bertotti "Ferromagnetic resonance and superparamagnetic behavior of iron oxide nanoparticles injected in porous anodic alumina" J. of Appl. Phys. 103, 07D527 (2008)
· S. Serrano-Guisan et al., Phys. Rev. Lett., 101, 087201 (2008)
· S. Serrano-Guisan et al., J. Phys D.: Appl. Phys. 41, 164015 (2008).
· D. Drung, J. Beyer, M. Peters, Th. Schurig; Novel SQUID curren sensors with high linearity at high frequencies, Invited talk at the ASC'08, Chicago,
· D. Drung, J. Beyer, M. Peters, Th. Schurig; Novel SQUID curren sensors with high linearity at high frequencies, accepted for publication in IEEE Trans. Appl. Supercond.
· invited talk related to L. Hao, J.C. Macfarlane, J.C. Gallop, D. Cox, J. Beyer, D. Drung, and T. Schurig; Measurement and noise performance of nano-superconducting-quantum-interference devices fabricated by focused ion beam; Appl. Phys. Lett. 92, 192507 (2008).
· Kazakova, R. Morgunov, J. Kulkarni, J. Holmes, and L. Ottaviano. 'Effect of dimensionality on the spin dynamics of GeMn systems: Electron spin resonance measurements'. Phys. Rev. B, 77, 235317 (2008).
· R. Morgunov, M.Farle, M. Passacantando, L. Ottaviano, and O. Kazakova. 'Electron Spin Resonance and Microwave Magnetoresistance in Ge:Mn Thin Films' Phys. Rev. B 78, 045206 (2008).
· M. I. van der Meulen, N. Petkov, M. A. Morris, O. Kazakova, X. Han, K. L. Wang, A. P. Jacobs, and J. D. Holmes, 'Single Crystalline Ge1-xMnx Nanowires as Building Blocks for Nanoelectronics'. Nano Lett., 9, 50 (2009).
· R. B. Morgunov, A. I. Dmitriev, Y. Tanimoto, and O. Kazakova, 'Electron spin resonance of charge carriers and antiferromagnetic clusters in Ge0.99Cr0.01 nanowires', J. Appl. Phys. In press. 105 (2009).
· I. Dmitriev, R. B. Morgunov, O. Kazakova, and Y. Tanimoto, 'Spin-wave resonance in GeMn thin films possessing percolation ferromagnetic ordering' J. Exp. And Theoretical. Physics. Russian version. Accepted. June 2009.
· L. Hao, D. C. Cox and J C Gallop, 'Characteristics of focussed ion beam nano Josephson devices' Superconducting Science and technology. Accepted. 2009.
· Kazakova, M. I. van der Meulen, N. Petkov, and J. D Holmes, Magnetic Properties of Single-Crystalline Ge1-xMnx Nanowires. Submitted to IEEE Trans. on Magn. (2009).
· Kazakova, J. C. Gallop, P. See, D. Cox, G. K. Perkins, J. D. Moore, and L. F. Cohen Detection of a micron-sized magnetic particle using InSb Hall sensor Submitted to IEEE Trans. on Magn. (2009).
· L. Fricke, S. Serrano-Guisan, H. W. Schumacher: “Parmeter dependence of resonant spin torque magnetization reversal” IEEE Trans. Magn., submitted (2009).
· K.-F. Braun, S. Sievers, M. Albrecht, U. Siegner, K. Landfester, V. Holzapfel “Stability of the magnetic domain structure of nanoparticle thin films against external fields” Journal of Magnetism and Magnetic Materials 321 (2009), pp. 3719-3725.
· O. Kazakova, R. Morgunov, J. Kulkarni, J. Holmes, and L. Ottaviano. ‘Effect of dimensionality on the spin dynamics of GeMn systems: Electron spin resonance measurements’. Phys. Rev. B, 77, 235317 (2008).
· R. Morgunov, M.Farle, M. Passacantando, L. Ottaviano, and O. Kazakova. ‘Electron Spin Resonance and Microwave Magnetoresistance in Ge:Mn Thin Films’ Phys. Rev. B 78, 045206 (2008).
· M. I. van der Meulen, N. Petkov, M. A. Morris, O. Kazakova, X. Han, K. L. Wang, A. P. Jacobs, and J. D. Holmes, 'Single Crystalline Ge1-xMnx Nanowires as Building Blocks for Nanoelectronics'. Nano Lett., 9, 50 (2009).
· R. B. Morgunov, A. I. Dmitriev, Y. Tanimoto, and O. Kazakova, ‘Electron spin resonance of charge carriers and antiferromagnetic clusters in Ge0.99Cr0.01 nanowires’, J. Appl. Phys. 105, 093922 (2009).
· A. I. Dmitriev, R. B. Morgunov, O. Kazakova, and Y. Tanimoto, ‘Spin-wave resonance in GeMn thin films possessing percolation ferromagnetic ordering’, J. Exp. and Theor. Phys. 108, p. 985 (2009).
· R. B. Morgunov, A. I. Dmitriev and O. L. Kazakova, ‘Percolation ferromagnetism and spin waves in Ge:Mn thin films’. Phys. Rev. B 80, 085205 (2009).
· I. Rod et al., O. Kazakova, D. C. Cox, M. Spasova, and M. Farle. ‘Route to single magnetic particle detection: carbon nanotube decorated with a finite number of nanocubes’, Nanotechnology 20, 335301 (2009).
· O. Kazakova, M. I. van der Meulen, N. Petkov, and J. D Holmes, ‘Magnetic Properties of Single-Crystalline Ge1-xMnx Nanowires’. IEEE Trans. on Magn. 45, 4085 (2009).
· O. Kazakova, R. Morgunov, A. Dmitriev, A. Chernenkaya, Y. Tanimoto, and L. Ottaviano, ‘Influence of Growth Temperature on the Percolation in Ge:Mn thin films’. Submitted to IEEE Trans. on Magn.
· O. Kazakova, J. C. Gallop, D. C. Cox, E. Brown, A. Cuenat, and K. Suzuki. ‘Optimization of 2DEG InAs/GaSb Hall Sensors for Single Particle Detection’. IEEE Tran. on Magn. 44, 4480 (2008).
· L. Hao, D. C. Cox and J C Gallop, ‘Characteristics of focussed ion beam nano Josephson devices’ Superconducting Science and technology. 22, 064011 (2009).
· O. Kazakova, J. C. Gallop, P. See, D. Cox, G. K. Perkins, J. D. Moore, and L. F. Cohen, Detection of a micron-sized magnetic particle using InSb Hall sensor. IEEE Trans. on Magn. 45, 4499 (2009).
· S. Serrano-Guisan, Han-Chun Wu, C. Boothman, M. Abid, I. V. Shvets, H. W. Schumacher: “Time-resolved precessional magnetization dynamics in Fe3O4 thin films by pulsed inductive microwave magnetometry” Appl. Phys. Lett., submitted (2010).
· K.-F. Braun, S. Sievers, D. Eberbeck, S. Gustafsson, E. Olsson, H.W. Schumacher, U. Siegner, ‘Quantitative measurement of the magnetic moment of an individual magnetic nanoparticle by magnetic force microscopy', Submitted to Nanotechnology.
· K.-F. Braun, S. Sievers, M. Albrecht, U. Siegner, K. Landfester, V. Holzapfel, ‘Stability of the magnetic domain structure of nanoparticle thin films against external fields ', Journal of Magnetism and Magnetic Materials 321 (2009), pp. 3719-3725.
· Michaela Kuepferling, Claudio Serpico , Matthew Pufall , William H. Rippard , T. Mitchell Wallis, , Atif Imtiaz , Pavol Krivosik , Massimo Pasquale , Pavel Kabos Two modes behavior of vortex oscillations in spin-transfer nano-contacts subject to in-plane magnetic fields Appl. Phys. Lett. in press June 2010
· O. Kazakova, V. Panchal, J. Gallop, P. See, D. C. Cox, M. Spasova, and L. F. Cohen, ‘Ultra-small particle detection using a nano-sized Hall sensor’. J. Appl. Phys. 107, 09E708 (2010).
· O. Kazakova, L. Hao, D. Cox, P. See, and J. Gallop, Magnetic nanoparticle detection using nano-SQUID sensors. Submitted to J. Phys. D.
· L. Hao, J. C. Gallop, O. Kazakova, D. Cox, C. Aßmann, F. Ruede, D. Drung, and Th. Schurig, Detection of Single Magnetic Nanobead with a nano-SQUIDs. Submitted to Appl. Phys. Lett.
Conferences
· O. Kazakova, V. Panchal, J. Gallop, P. See, D. C. Cox, M. Spasova, and L. F. Cohen, ‘Ultra-small particle detection using a nano-sized Hall sensor’. Submitted to J. Appl. Phys.
· Magnetic Properties of Single-Crystalline Ge1-xMnx Nanowires O. Kazakova, M. I. van der Meulen, N. Petkov, and J. D Holmes INTERMAG 2009
· Detection of a micron-sized magnetic particle using InSb Hall sensor O. Kazakova, J. C. Gallop, P. See, D. Cox, G. K. Perkins, J. D. Moore, and L. F. Cohen INTERMAG 2009
· Doublet sub-GHz peaks in the spectra of magnetization oscillations in spin-transfer nanocontacts. M. Kuepferling1, C. Serpico2, M. R. Pufall3, M. T.Wallis3, R. Heindl3, H. Nembach3, W. H. Rippard3, A. Imtiaz3, M.Pasquale1, P. Kabos3 INTERMAG 2009
· Hard transitions to magnetic vortex self-oscillations in spin-transfer nanocontacts. M. T.Wallis, C. Serpico, M. Kuepferling, H. Nembach, M. R. Pufall, W. H. Rippard, A. Imtiaz, M. Pasquale, P. Krivosik, P. Kabos INTERMAG 2009
· Presentation at SMM Conference Torino Sept. 2009: Structural characteristics and magnetic properties of Fe oxide nanoparticles M. Pasquale, E. Olivetti, P. Rizzi, V. A. Coleman, J. Herrmann (NMI Lindfield NSW Australia)
· M. Pasquale Presentation at the National Conference on Magnetism Roma Oct. 2009 FUNCTIONALIZED MAGNETIC NANOPARTICLES FOR BIOLOGICAL APPLICATIONS
· A tutorial on "Integration of Magnetoelectronics with CMOS" has been arranged and an invited symposium on the same topic was organized within the 2009 Intermag Conference sponsored by the IEEE Magnetics Society (May 2009 Sacramento, Ca Conference Chairman M. Pasquale). www.intermagconference.com
· Presentation to Intermag Conference Sacramento CA: ER-07. Doublet sub-GHz peaks in the spectra of magnetization oscillations in spin-transfer nanocontacts. M. Kuepferling 1, C. Serpico2, M.R. Pufall3, M.T.Wallis3, R. Heindl3, H. Nembach3, W.H. Rippard3, A. Imtiaz3, M. Pasquale1 and P. Kabos3 1. INRiM Torino, Italy; 2. University of Naples Federico II, Napoli, Italy; 3. NIST, Boulder, CO, USA
· Presentation to Intermag Conference Sacramento CA: GD-10. Hard transitions to magnetic vortex selfoscillations in spin-transfer nanocontacts. M.T.Wallis 1,C. Serpico2, M. Kuepferling3, H. Nembach1, M.R. Pufall1, W.H. Rippard1, A. Imtiaz1, M. Pasquale3, P. Krivosik4 and P. Kabos1 1. NIST, Boulder, CO, USA; 2. Università di Napoli “Federico II”; 3. INRiM, Torino, Italy; 4. Colorado State University
· Presentation at SMM Conference Torino Sept. 2009: Analysis of field-induced asymmetric switching in nanopillar devices Paolo Bortolotti, Michaela Kuepferling, Massimo Pasquale
· Presentation at SMM Conference Torino Sept. 2009: Magnetization properties of FeTb thin films A. Magni, F. Celegato, M. Coisson, E.S. Olivetti, M. Pasquale, C.P. Sasso (to be published on IEEE Trans. Mag.)
· Presentation at SMM Conference Torino Sept. 2009: Ferromagnetic resonance and damping in soft magnetic films: measurements and intercomparison M. Pasquale, G. Bertotti, E. Olivetti, M. Coisson, F. Celegato, Y. Endo,Y. Mitsuzuka, M. Yamaguchi, S. Serrano-Guisan, H.W.Schumacher, P. Kabos
· “Quasi Ballistic Spin Torque Magnetization Reversal”
· S. Serrano-Guisan, K. Rott, G. Reiss, J. Langer, B. Ocker, and H. W. Schumacher, Invited talk, SPIE Optics & Photonics Conference, August 2009, San Diego, USA.
· “Traceable measurement of the magnetization of magnetic nanoparticles by magnetic force microscopy” K.-F. Braun, S. Sievers, L. Trahms, H.W. Schumacher: Accepted for Joint MMM / Intermag Conference 2010, Washington, USA.
· “Tunnel barrier thickness dependence of the free layer magnetization dynamics in CoFeB/MgO/CoFeB based magnetic tunnelling junctions” S. Serrano-Guisan, W. Skowronski, J. Wrona, M. Czapkiewicz, t. Stobiecki, J. Langer, B. Ocker, G. Reiss, H.W. Schumacher: Accepted for Joint MMM / Intermag Conference 2010, Washington, USA.
· “Parameter dependence of the spin transfer torque in magnetic tunnel junctions measured by time resolved magneto transport” S. Serrano-Guisan, K. Rott, G. Reiss, J. Langer, B. Ocker, and H. W. Schumacher MMM Conference 2008, November 2008, Austin, USA.
· “Readout of Nano SQUIDs” Frank Ruede, Cornelia Aßmann, Jörn Beyer, Thomas Schurig, Olga Kazakova, Ling Hao, John Gallop, Poster presented at workshop Kryoelektronische Bauelemente 2009” held October 4-6 in Oberhof, Germany.
· “Improvement of the spin torque reversal by resonant microwave currents” Lukas Fricke, Santiago Serrano-Guisan, Hans-Werner Schumacher, Poster, DPG Spring Meeting, March 2009, Dresden, Germany.
· O. Kazakova et al. Intermag (May 2009, Sacramento, CA). Oral. ‘Single-crystalline Ge1-xMnx nanowires for nanoelectronic applications’.
· O. Kazakova et al. (December 2009, Warwick, UK). Poster. ‘Percolation nature of magnetic ordering in Ge:Mn’.
· O. Kazakova et al. (January 2010, Washington, US). Oral. ‘Percolation ferromagnetism in Ge:Mn thin films’.
· O. Kazakova et al. Intermag (May 2009, Sacramento, CA). Oral. ‘Detection of a micron-sized magnetic particle using InSb Hall sensor’.
· M. Bratko, et al. UK SPM (June 2009, Teddington, UK). Poster. ‘A Route To Traceable Calibration of Magnetic Probes’. 2nd prize.
· L. Hao et al. (December 2009, Warwick, UK). Oral. ‘NanoSQUIDs for FePt magnetic nanoparticle detection'.
· O. Kazakova et al. (December 2009, Warwick, UK). Oral. ‘Detection of a single FePt nanoparticle using small Hall sensor’.
· O. Kazakova et al. (January 2010, Washington, US). Oral. ‘Ultra-small particle detection using a nano-sized Hall sensor’.
· O.Kazakova Joint Intermag – MMM conference. Oral. January 2010. Washington, DC.
· O.Kazakova ICFPM. Invited. June 2010. Uppsala, Sweden.
· O.Kazakova ASC. Oral. August 2010. Washington, DC.
· M. Pasquale ICMM Boston June 2010 Invited
· M. Pasquale CPEM 2010 Daejon Oral
· S. Sievers, K.-F. Braun, D. Eberbeck, and H.W. Schumacher, ‘Quantitative analysis of the magnetic moments of individual magnetic nanoparticles by magnetic force microscopy’, Joint MMM-INTERMAG 2010
· “Optimum tunnel barrier thickness for spin torque memory devices” S. Serrano-Guisan, W. Skowronski, N. Liebling, J. Wrona, M. Czapkiewicz, T. Stobiecki, J. Langer, B. Ocker, G. Reiss, H.W. Schumacher: Poster, DPG Spring Meeting, March 2010, Regensburg, Germany.
· “Traceable measurement of the magnetization of magnetic nanoparticles by magnetic force microscopy” K.-F. Braun, S. Sievers, L. Trahms, H.W. Schumacher: Talk, Joint MMM / Intermag Conference 2010, Washington, USA.
· “Tunnel barrier thickness dependence of the free layer magnetization dynamics in CoFeB/MgO/CoFeB based magnetic tunnelling junctions” S. Serrano-Guisan, W. Skowronski, J. Wrona, M. Czapkiewicz, t. Stobiecki, J. Langer, B. Ocker, G. Reiss, H.W. Schumacher: Talk, Joint MMM / Intermag Conference 2010, Washington, USA.
·
Presentations:
· O. Kazakova. (April 2009, at NTT, Tokyo, Japan). Invited seminar on magnetic nano-sensors.
· J. Gallop (May 2009, at PTB, Berlin (+videoconference transmitting to Braunschweig, Germany) ‘ SQUID metrology’.
· invited talks of Olga Kazakova NPL at MISM, ECOSS 25, Intel Forum and FNMA’09.
· In May 2009 John Gallop from NPL has visited PTB Berlin to discuss current joint activities. He gave a talk about SQUID metrology which was also transmitted in a video conference to PTB Braunschweig.
· Visit of H.W. Schumacher to Thales Group, Orsay (A. Fert) for talk on spin torque dynamics and discussion.
· Visit and talks of H. W. Schumacher at Singulus AG 12/2008 and Hitachi, Cambridge 2/2009
· A presentation of the NanoSpin activities was given at the EURAMET meeting on DC&Quantum Metrology held in Paris (M. Pasquale, June 2009, Paris)
· EURAMET meeting on DC&Quantum Metrology M. Pasquale KRISS Daejon June 2010
