Nanoscale Magnetic Materials - Magnetic Domains

Projects

Multifunctional magnetooptical sensors

Magnetooptical sensors for the measurements of magnetic fields, electrical quantities, and temperature​

MO Sensing Challenges for the applications of magnetic sensors vary greatly. In addition to the regular measurements of magnetic field quantities an important field of application of magnetic sensors is the indirect measurement of electrical quantities, in particular the electrical current. The aim of the project is to investigate multifunctional magnetooptical sensor elements that allow simultaneous optical measurements of additional functional parameters, in particular the measurement of temperatures. This will be achieved using magnetooptically active ferrimagnetic garnet layers. The read-out scheme is based on the temperature dependence of saturation magnetization and thus the corresponding variation of the magnetooptical Faraday and Voigt effect. Especially challenging is the envisioned reduction of magnetic hysteresis effects, which so far limit the overall sensitivity of the sensors. By influencing the effective pinning behavior of the domain walls, the sensitivity of the sensors will be enhanced. All studies are supported by in-operando magnetic domain observations. An essential part of the investigations is devoted to basic research on the various sensor mechanisms and the unraveling of the different signal influences for the simultaneous measurement of the respective quantities. The question of whether optical, local, and simultaneous measurements of quantities like temperature, magnetic field strength, and electric current can be detected with a single multifunctional sensor is at the center of the project. Such broadband and optical readout sensors could decisively alter measurement methods to ensure the operational safety in electrical systems. The investigation of methods for reducing the effective magnetic hysteresis by external stimuli is also of relevance for a variety of other sensor applications and thus well beyond the use of garnet layers as sensor elements.
 

Mulitfuctional magnetooptical sensors at DFG Gepris.

  1. N.O. Urs, B. Mozooni, P. Mazalski, M. Kustov, P. Hayes, S. Deldar, E. Quandt, J. McCord, Advanced magneto-optical microscopy: Imaging from picoseconds to centimeters - imaging spin waves and temperature distributions (invited), AIP Advances 6, 055605 (2016)
  2. M. Kustov, R. Grechishkin, M. Gusev, O. Gasanov, J. McCord,  A novel scheme of thermographic microimaging using pyro-magneto-optical indicator films, Advanced Materials 27, 5017–5022 (2015) 

Domain wall dynamics

Domain wall dynamics and magnetic texture behavior in magnetic films with Dzyaloshinskii-Moriya interaction

Magnetic structures, like chiral domain walls, and topological structures, like vortices and skyrmions, are the foundation for future solid state magnetic information technologies. A variety of theoretical studies predict intriguing phenomena for the propagation of micromagnetic objects in such structures. The goal of the project is to obtain a fundamental understanding of the manipulation of micromagnetic structures in connection with static and dynamic properties of magnetic thin films. The focus of the project is on the investigation of the high-frequency response of nearly free magnetic heterostructures to external stimuli. Epitaxial thin film systems with variable magnetic anisotropy contributions and confined spin structures will be spanned and magnetic field, thermo-optical, and spin current induced magnetization dynamics will be investigated by combined high temporally and high spatially resolved imaging methods. The investigations of the tailored structures are backed by complementary magnetic property measurements and micromagnetic calculations. Combining simulations and time resolved real-time imaging will clarify the underlying physical mechanisms. The research will provide a fundamental contribution to the realization of envisioned new memory technologies.
 

Domain wall dynamics at DFG Gepris.

Manipulation of magnetic microbeads

Magnetic surfaces for the controlled manipulation of superparamagnetic microbeads

Moving beadThe manipulation of superparamagnetic microbeads with functionalized surfaces as labels for single-molecule studies, for cell manipulation, and detection of chemical or biological species in liquid environments are in the focus of the research project. Within the project the fundamentals for the movement of superparamagnetic beads on functionalized magnetic surfaces will be explored. As a basis for the manipulation of beads, micro-lithographically patterned magnetic surfaces in the form of array elements creating an interconnecting magnetic network will be investigated. The transport of individual beads is performed by micro-magnetic objects such as charged magnetic domain walls and switchable magnetization structures. 

Within the project the controlled movement of microbeads along magnetic structures with the help of variable multi-axis magnetic field protocols will be investigated. Different approaches are being explored for the transport of superparamagnetic particles in liquid suspensions. Moreover, hydrodynamic effects will be utilized by applying temporal and angle varying magnetic fields with different frequency components. The investigations will be supported by a combination of micro-magnetic and magnetic stray field simulations. The lateral distribution of the magnetic patterns and the corresponding motion of the microbeads are analyzed directly by complementary in-situ magnetic and bright-field optical microscopy. 

The research will open up new ways to laterally manipulate marked biological objects, to facilitate a controlled movement of particles in microfluidic environments over substantial distances, and in that way provide the foundations for the manipulation and separation of biological objects in integrated flowless lab-on-chip devices.

Magnetic surfaces at DFG Gepris.

  1. U. Sajjad, R.B. Holländer, F. Klingbeil, J. McCord, Magnetomechanics of superparamagnetic beads on a magnetic Merry-Go-Round: from micromagnetics to radial looping, Journal of Physics D: Applied Physics 50, 135003 (2017) 

Domain configurations and magnetization dynamics

Adjustable and switchable magnetic high-frequency properties - domain configurations and observation of magnetization dynamics of structured ferromagnetic layersFeCoSiB@3GHz

The project focuses on the correlation of artificially generated magnetic domains and domain wall configurations with the magneto-dynamic response in magnetic micro-and nanostructured thin films. Large area thin film nanoscale structures and thus novel effective magnetic media will be produced, the effective magnetic properties of which will be varied by different imprinted magnetization configurations. The variable remanent magnetization configurations are set by periodic nanostructures and magneto-thermal methods. Different approaches to the fabrication of domain engineered structures will be studied. Using various methods of domain control, novel ways to adjust the magnetic permeability and the spin-wave behavior of magnetic structures will be investigated.

Essentially, new principles for optimized functionality in the area of magnetic sensors and magnetization dynamics are created. The main focus of the current studies is on switchable magnetic high-frequency characteristics of large surface nanoscale structures.

Adjustable high-frequency properties at DFG Gepris.

References

  1. M. Lohman, B. Mozooni, J. McCord, Homogeneous microwave field emitted propagating spin waves: Direct imaging and modeling, Journal of Magnetism and Magnetic Materials 450, 7 (2018) 
  2. R.B. Holländer, C. Müller, M. Lohmann, B. Mozooni, J. McCord, Component selection in time-resolved magneto-optical wide-field imaging for the investigation of magnetic microstructures, Journal of Magnetism and Magnetic Materials 432, 283–290 (2017)
  3. B. Mozooni, J. McCord, Direct observation of closure domain wall mediated spin-waves, Applied Physics Letters 107, 042402 (2015) 
  4. B. Mozooni, T. von Hofe, J. McCord, Picosecond wide-field magneto-optical imaging of magnetization dynamics of amorphous film elements, Physical Review B 90, 054410 (2014)
  5. C. Hengst, M. Wolf, R. Schäfer, L. Schultz, J. McCord, Acoustic-domain resonance mode in magnetic closure-domain structures: A probe for domain-shape characteristics and domain-wall transformations, Physical Review B 89, 214412 (2014) 
  6. C. Hamann, R. Mattheis, I. Mönch, J. Fassbender, L. Schultz, J. McCord, Magnetization dynamics of magnetic domain wall imprinted magnetic films, New Journal of Physics 16, 023010 (2014)
  7. J. McCord, S. Mangin,  Separation of low- and high-temperature contributions to the exchange bias in Ni81Fe19-NiO thin films,  Physical Review B 88, 014416  (2013) 
  8. C. Patschureck, K. Lenz, M. O. Liedke, M. U. Lutz, T. Strache, I. Mönch, R. Schäfer, L. Schultz, and J. McCord, Magnetization dynamics of buckling domain structures in patterned thin films, Physical Review B 86, 054426 (2012)

 

Magnetic domains in magneto-electric composites

ME-composite-small

Magnetic domain effects in magneto-electric composite materials

The aim of the project is to investigate and optimize the magnetic domain structure in magneto-electric composites. Using spatially resolved characterization methods, we plan to obtain an understanding of the magnetic rearrangement processes in magneto-electric thin films. From this, concepts for the control of the magnetic domain behavior will be developed with the objective of achieving the largest effective magnetostriction or permeability. In addition, the mechanism of interaction between magnetostrictive and piezoelectric materials will be investigated. The studies are supported by comparative modeling of the magnetization reversal behavior. The investigations form a basis for the understanding of magnetoelectric composite behavior.

Magnetoelectric sensor domains at DFG Gepris

CRC 1261- Magnetoelectric Sensors: From Composite Materials to Biomagnetic Diagnostics

 

References

  1. A. Kittmann, P. Durdaut, S. Zabel, J. Reermann, J. Schmalz, B. Spetzler, D. Meyners, N.X. Sun, J. McCord, M. Gerken, G. Schmidt, M. Höft, R. Knöchel, F. Faupel, E. Quandt, Wide Band Low Noise Love Wave Magnetic Field Sensor System, Scientific Reports 8, 278 (2018)
  2. V. Röbisch, S. Salzer, N. Urs, J. Reermann, E. Yarar, A. Piorra, C. Kirchhof, E. Lage, M. Höft, G. Schmidt, R. Knöchel, J. McCord, E. Quandt, D. Meyners, Pushing the detection limit of thin film magnetoelectric heterostructures, Journal of Materials Research 1-11 (2017)
  3. M. Abes, C. T. Koops, S. B. Hrkac, J. McCord, N. O. Urs, N. Wolff, L. Kienle, W. J. Ren, L. Bouchenoire, B. M. Murphy, O. M. Magnussen. Domain structure and reorientation in CoFe2O4, Phys. Rev. B 93, 195427 (2016) 
  4. N.O. Urs, B. Mozooni, P. Mazalski, M. Kustov, P. Hayes, S. Deldar, E. Quandt, J. McCord, Advanced magneto-optical microscopy: Imaging from picoseconds to centimeters - imaging spin waves and temperature distributions (invited), AIP Advances 6, 055605 (2016)
  5. V. Röbisch, E. Yarar, N. O. Urs , I. Teliban, R. Knöchel, J. McCord, E. Quandt, D. Meyners, Exchange biased magnetoelectric composites for magnetic field sensor application by frequency conversion, Journal of Applied Physics 117, 17B513 (2015)
  6. N. O. Urs, I. Teliban, A. Piorra, R. Knöchel, E. Quandt, J. McCord, Origin of hysteretic magnetoelastic behavior in magnetoelectric 2-2 composites, Applied Physics Letters 105, 202406 (2014)
  7. V. Hrkac, E. Lage, G. Köppel, J. Strobel, J. McCord, E. Quandt, D. Meyners, L. Kienle, Amorphous FeCoSiB for exchange bias coupled and decoupled magnetoelectric multilayer systems: Real-structure and magnetic properties, Journal of Applied Physics 116, 134302 (2014)
  8. E. Lage, N. O. Urs, V. Röbisch, I. Teliban, R. Knöchel, D. Meyners, J. McCord, E. Quandt, Magnetic domain control and voltage response of exchange biased magnetoelectric composites, Applied Physics Letters 104, 132405 (2014)
  9. T. von Hofe, N. O. Urs, B. Mozooni, T. Jansen, C. Kirchhof, D. E. Bürgler, E. Quandt, J. McCord, Dual wavelength magneto-optical imaging of magnetic thin films, Applied Physics Letters 103, 142410 (2013) 
  10. S. B. Hrkac, M. Abes, C. T. Koops, C. Krywka, M. Müller, S. Kaps, R. Adelung, J. McCord, E. Lage, E. Quandt, O. M. Magnussen, and B. M. Murphy,  Local magnetization and strain in single magnetoelectric micorrod composites,  Applied Physics Letters 103,  123111  (2013) 

 

Hybrid magnetic materials (finished project)

Advanced Materials

Hybrid magnetic materials - microscopic modifications resulting in macroscopic effects

Understanding the correlation of artificial magnetic domain configurations and effective magnetic characteristics, such as the anisotropy, exchange coupling, and interlayer exchange coupling is the main goal of the research project. Artificial magnetic structures are produced with the aid of ion irradiation techniques in order to modify magnetic characteristics on a length scale comparable to or below the magnetic characteristic correlation lengths. By this, completely new domain wall and domain configurations are imprinted that do not occur in conventional film systems. With the progressive reduction in structure size materials with modified effective magnetic properties, so-called magnetic hybrid materials, are generated. 

The current focus of the project is on the investigation of the functional relationship between microscopic magnetic property patterns and the integrally measured effective magnetic parameters. The scalability of the findings are examined by the comparison of different material systems with varying effective magnetic correlation lengths.

Hybrid magnetic materials project at DFG Gepris 

References

  1. J. Osten, K. Lenz, H. Schultheiss, J. Lindner, J. McCord, J. Fassbender, Interplay between magnetic domain patterning and anisotropic magnetoresistance probed by magneto-optics, Physical Review B 97, 014415 (2018)
  2. J. Trützschler, K. Sentosun, B. Mozooni, R. Mattheis, J. McCord. Magnetic domain wall gratings for magnetization reversal tuning and confined dynamic mode localization, Scientific Reports 6, 30761 (2016) 
  3. J. Trützschler, K. Sentosun, M. Langer, I. Mönch, R. Mattheis, J. Fassbender, J. McCord, Optimization of magneto-resistive response of ion-irradiated exchange biased films through zigzag arrangement of magnetization, Journal of Applied Physics 115, 103901 (2014) 
  4. M. Langer, A. Neudert, I. Mönch, R. Mattheis, K. Lenz, J. Fassbender, J. McCord, Magneto-optical analysis of stripe elements embedded in a synthetic antiferromagnet, Physical Review B 89, 064411 (2014) 
  5. O. D. Roshchupkina, J. Grenzer, T. Strache, J. McCord, M. Fritzsche, A. Muecklich, C. Baehtz, and J. Fassbender, Focused ion beam induced structural modifications in thin magnetic films, Journal of Applied Physics 112, 033901 (2012)  
  6. A. Maziewski, P. Mazalski, Z. Kurant, M. O. Liedke, J. McCord, J. Fassbender, J. Ferré, A. Mougin, A. Wawro, L. T. Baczewski, A. Rogalev, F. Wilhelm, and T. Gemming, Tailoring of magnetism in Pt/Co/Pt ultrathin films by ion irradiation, Phys. Rev. B 85, 054427 (2012)
  7. J. McCord, T. Strache, I. Mönch, R. Mattheis, J. Fassbender, Spatial manipulation of magnetic damping in ferromagnetic-antiferromagnetic films by ion irradiation, Physical Review B 83, 224407 (2011)
  8. A. Vogel, S. Wintz, T. Gerhardt, L. Bocklage, T. Strache, M.-Y. Im, P. Fischer, J. Fassbender, J. McCord, G. Meier, Field- and current-induced domain-wall motion in permalloy nanowires with magnetic soft spots, Applied Physics Letters 98, 20250 (2011)
  9. N. Martin, I. Mönch, R. Schäfer, J. Fassbender, L. Schultz, J. McCord, Influence of dipolar energy on the magnetization reversal in magnetization-modulated thin film systems: Model and experiment, Physical Review B 83, 174423 (2011)
  10. J. Fassbender, T. Strache, M.O. Liedke, D. Markó, S. Wintz, K. Lenz, A. Keller, S. Facsko, I. Mönch, J. McCord, Introducing arti?cial length scales to tailor magnetic properties, New Journal of Physics, New Journal of Physics 11, 125002/1-19 (2009)
  11. N. Martin, J. McCord, A. Gerber, T. Strache, T. Gemming, I. Mönch, N. Farag, R.Schäfer, J. Fassbender, E. Quandt, L. Schultz, Local stress engineering of magnetic anisotropy in soft magnetic thin films, Applied Physics Letter 94, 062506 (2009)
  12. J. McCord, I. Mönch, J. Fassbender, A. Gerber, E. Quandt, Local setting of magnetic anisotropy in amorphous Films by Co ion implantation, J. Phys. D 42, 055006 (2009)
  13. J. Fassbender, J. McCord, Magnetic patterning by means of ion irradiation and implantation (Review), Journal of Magnetism and Magnetic Materials 320, 579 (2008)
  14. J. McCord, L. Schultz, J. Fassbender, Hybrid soft-magnetic lateral exchange spring films prepared by ion irradiation, Advanced Materials 20, 2090 (2008)
  15. J. Fassbender, J. von Borany, A. Mücklich, K. Potzger, W. Möller, J. McCord, L. Schultz, R. Mattheis, Structural and magnetic modifications of Cr-implanted permalloy, Physical Review B 73, 184410 (2006)
  16. J. Fassbender, J. McCord, Control of saturation magnetization, anisotropy, and damping due to Ni implantation in thin Ni81Fe19 layers, Applied Physics Letters 88, 252501 (2006)
  17. K. Potzger, L. Bischoff, M. O. Liedke, B. Hillebrands, M. Rickart, P. P. Freitas, J. McCord, J. Fassbender, Domain structure of magnetically micro-patterned PtMn/NiFe exchange biased bilayers, IEEE Trans. Magn. 41, 3610 (2005)
  18. J. McCord, J. Fassbender, M.O. Liedke, M. Frommberger, T. Gemming, E. Quandt, L. Schultz, Magnetic anisotropy and domain patterning of amorphous films by He-ion irradiation, Applied Physics Letters 86, 162505 (2005)

 

Magnetic shape memory alloys (finished project)

MSMA domains small

Dynamic metallographic and magneto-optical polarization microscopy of magnetic shape memory alloy systems (completed)

Time-resolved metallographic optical microscopy techniques together with magnetic domain imaging are used to clarify the interaction between magnetic domains and twin boundary motion in magnetic shape memory alloy single crystals. The magnetic field and stress induced magnetic domain formation can be imaged by a magneto-optical indicator film technique. Thereby reversible twin boundary motion can be visualized up to high actuation speeds. 

For instance, from domain observations at adjacent crystal surfaces we have derived the fundamental volume magnetic processes during strain and field induced twin boundary motion. One of the main results is the discovery of magnetic field induced structural reorientations without concurrent magnetic domain wall motion. On the contrary, for strain induced reorientations processes a complete rearrangement of the magnetic domain structure by the moving twin boundaries is observed. 

From dynamic actuation experiments on twin boundary motion we found that the field induced strain increases with actuation speed, resulting in non-linear time effects on twin boundary mobility. The findings can be interpreted as the interaction of moving twin boundaries with local non-fixed defects. The results provide key information for the understanding of the connection of magnetic and crystallographic domains in magnetic shape memory alloys as well as for the optimization of devices for future technical applications.

MSM project at DFG Gepris

References 

  1. A. Neudert, Y. W. Lai, R. Schäfer, M. Kustov, L. Schultz, J. McCord, Magnetic Domains and Twin Boundary Movement of NiMnGa Magnetic Shape Memory Crystals, Advanced Engineering Materials 14, 601–613 (2012)
  2. Y.-W. Lai, R. Schäfer, L. Schultz, J. McCord, Volume magnetic domain mirroring in magnetic shape memory crystals, Applied Physics Letters 96, 22507 (2010)
  3. N. Scheerbaum, Y.W. Lai, T. Leisegang, M. Thomas, J. Liu, K. Khlopkov, J. McCord, S. Faehler, R. Traeger, D.C. Meyer, L. Schultz, O. Gutfleisch, Constraint-dependent twin variant distribution in Ni2MnGa single crystal, polycrystals and thin film: An EBSD study, Acta Materialia 58, 4629-4638 (2010)
  4. M. Thomas, O. Heczko, J. Buschbeck, Y.W. Lai, J. McCord, L. Schultz, S. Fähler, Stray field induced actuation mode of freestanding magnetic shape memory films, Advanced Materials, 21, 3708, (2009)
  5. Y.-W. Lai, R. Schäfer, L. Schultz, J. McCord, Direct observation of AC field-induced twin-boundary dynamics in bulk NiMnGa, Acta Materialia 56, 5130 (2008)
  6. Y.W. Lai, N. Scheerbaum, D. Hinz, O. Gutfleisch, R. Schäfer, L. Schultz, J. McCord, Absence of magnetic domain wall motion during magnetic field induced twin boundary motion in bulk magnetic shape memory alloys, Applied Physics Letters 90, 192504 (2007)