The present research leading to PhD involves the growth and properties of ferromagnets on semiconductor substrates. The work deals with three important aspects: (i) growth and structural characterization, (ii) magnetic properties, and (iii) magnetotransport properties of Fe and Fe₃Si films on low-symmetric GaAs(113)A substrates. These two ferromagnetic metals, namely Fe and Fe₃Si have cubic crystal structure and exhibit a close lattice match with GaAs. This allows to stabilize the [113]-orientation of the films on GaAs(113)A by using molecular-beam epitaxy (MBE). The structural properties of the Fe and Fe₃Si films are studied using techniques such as reflection high-energy electron diffraction (RHEED), high-resolution X-ray diffraction (HXRD), X-Ray Reflectivity (XRR), and Atomic force microscopy (AFM). The magnetic properties are studied by in-situ Magneto-optical Kerr effect, SQUID magnetometry, and different magnetotrantranport techniques such as anisotropic magnetoresistance, planar Hall effect (PHE) and anomalous Hall effect.  The basic achievements of this work include the following: (i) establishment of the growth of Fe and Fe₃Si on the high-index surface of GaAs(113)A substrates by MBE, (ii) study of the magnetic properties on the low-symmetric surface, which also provide the understanding to the incompletely understood uniaxial magnetic anisotropy (UMA) of Fe/GaAs system, (iii) substantiate correlation between structural and magnetic properties, and (iv) an important finding of an antisymmetric component in the PHE due to the reduced symmetry of the [113] orientation, (v) development of a phenomenological model based on the symmetry of the crystal  to understood the understand the observation of the antisymmetric component in PHE. The antisymmetric component in PHE is a completely new observation and to our knowledge is a first observation of the second-order Hall effect.

Research Highlights

Fe/GaAs(113)A:

Onset of Ferromagnetism

Evolution of Magnetic anisotropy

Antisymmetric contribution to the planar Hall effect

Fe₃Si/GaAS(113)A

Growth optimization and basic magnetic Properties

Publications  

• J. Herfort, H.-P. Sch�nherr, P. K. Muduli, and K. H. Ploog, Magnetic anisotropy of ultrathin epitaxial Fe films grown on As terminated GaAs(001)-2�1 substrates, in International Symposium on Compound Semiconductors: Post-Conference Proceedings, edited by M. R. Melloch and C. Tu,, pages 96, 101, IEEE, Piscataway, 2004.

• P. K. Muduli, J. Herfort, H.-P. Sch�nherr, and K. H. Ploog, Evolution of magnetic anisotropy and spin-reorientation transition in Fe films grown on GaAs(113)A substrates by molecular beam epitaxy, J. Appl. Phys. 97 123904 (2005) (7 pages)

• P. K. Muduli, J. Herfort, L. D�weritz, H.-P. Sch�nherr,, and K. H. Ploog, Magnetic anisotropy of Fe films on GaAs(113)A substrates, Appl. Phys. A, 81 901 (2005) (Rapid Communications)  (6 pages)[PDF]

• K.-J. Friedland, J. Herfort, P. K. Muduli, H.-P. Sch�nherr, and K. H. Ploog, Planar Hall effect in epitaxial Fe layers on GaAs(001) and GaAs(113)A substrates, Journal of Superconductivity, In Press on line at http://dx.doi.org/10.1007/s10948-005-0002-5

• P. K. Muduli, K.-J. Friedland, J. Herfort, H.-P. Sch�nherr, and K. H. Ploog, Anti-symmetric contribution to the planar Hall effect of Fe₃Si films grown on GaAs(113)A substrates, Phys. Rev. B 72, 104430 (2005) (9 pages)

• P. K. Muduli, J. Herfort, H.-P. Sch�nherr, and K. H. Ploog,  Epitaxial Fe₃Si films stabilized on GaAs(113)A substrates, J. Cryst. Growth, 285, 508 (2005) (7 pages).

• P. K. Muduli, J. Herfort, H.-P. Sch�nherr, and K. H. Ploog, Strong dependence of growth conditions on magnetic anisotropy of epitaxial Fe₃Si films on GaAs(113)A substrates, (In preparation).

• P. K. Muduli, J. Herfort, H.-P. Sch�nherr, and K. H. Ploog, Influence of atomic disorder on magnetic anisotropy of Fe₃Si films grown on GaAs(113)A substrates, (In preparation).

• P. K. Muduli, J. Herfort, K.-J. Friedland, H.-P. Sch�nherr, and K. H. Ploog, Study of magnetization reversal by planar Hall effect of Fe and Fe₃Si films grown on GaAs(113)A substrates (In preparation).

   

Conference contributions

• K. J. Friedland, P. K. Muduli, J. Herfort, H.-P. Sch�nherr, and K. H. Ploog, Planar Hall effect in epitaxial Fe layers on GaAs(001) and GaAs(113)A substrates, 3rd International Conference on Physics and Applications of Spin-Related Phenomena in Semiconductors (PASPS III), Santa Barbara (USA), July 21-23 (2004)

• J. Herfort, , H.-P. Sch�nherr, P.K. Muduli, and K.H.Ploog, Magnetic anisotropy of ultrathin epitaxial Fe films grown on As terminated GaAs(001)-2�1 substrates, 30^th International Symposium on compound semiconductors (ISCS-2003), San Diego, (USA), 25-27 August 2003

• K. J. Friedland, M.Bowen, J. Herfort, P. K. Muduli, H. -P. Sch�nherr, and K. H. Ploog, Intrinsic contributions to the planar Hall effect in epitaxial Fe and Fe₃Si films on GaAs substrates, 11^th Advanced Heterostructure Workshop, Kohala Coast (USA), December 5-10(2004)

• P. K. Muduli, J. Herfort, H.-P. Sch�nherr, and K.H.Ploog,  Magnetic properties of Fe and Fe₃Si films on GaAs(113)A substrates 338. WE-Heraeus-Seminar: Nanomagnetism: New Insights with Synchrotron Radiation, Bad Honnef, January 05 � 07 (2005).

Last Updated Wednesday February 08, 2006