MAGNETISM AND TWO-BAND TRANSPORT IN MNAS EPILAYERS

L. B. STEREN, J. MILANO, C. HELMAN, A. M. LLOIS, M. MARANGOLO, M. EDDRIEF, V. H. ETGENS

Francia

Congreso; Gordon Conference on Magnetic Nanostructures; 2008

Gordon Conferences

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} p.MsoPlainText, li.MsoPlainText, div.MsoPlainText {margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Courier New"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:35.4pt; mso-footer-margin:35.4pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Metallic MnAs is a promising material for uses in semiconductor-based spintronic devices. In fact, bulk MnAs is ferromagnetic at room temperature and has an hexagonal structure (alpha) whose lattice parameters match very well with those of GaAs. The MnAs undergoes a first order transition at T*=40 C between the low temperature hexagonal ferromagnetic phase and a paramagnetic orthorhombic one. The structural and magnetic properties of MnAs films are strongly affected by growth conditions and substrate. In this work we present a study of the magnetoresistance and Hall effect of ferromagnetic MnAs thin films. MnAs epilayers were grown by MBE onto GaAs(100) substrates. The magnetotransport properties have been measured with the electrical currente oriented along the hard-axis magnetization and perpendicular to it, in the plane of the films.  The low-temperature behavior of the magnetoresistance and the Hall effect curves can be  described by a two-band model that takes into account the contributions of holes and electrons-like orbits at the Fermi surface.   The temperature dependence of the ordinary Hall constant and the transverse magnetoresistance allow us to identify a transition between electron- and hole-dominated transport regimes.   The experimental results are discussed in terms of the electronic band structure and Fermi surface of the compound calculated by LAPW.