Magnetic Anisotropy And Magnetization Reversal In Ga1-Xmnxas Layers Studied By Polarized Neutron Reflectometry

The magnetic anisotropy and the in-plane magnetization reversal mechanism of Ga0.945Mn0.055As thin films, grown on GaAs(001), were investigated. Samples A and B, with sample A grown 45 degrees C lower than sample B, were analyzed by magnetization hysteresis measurements and polarized neutron reflectivity (PNR) magnetization reversal experiments. Magnetization hysteresis loops and temperature-dependent magnetization curves accounted for an in-plane uniaxial magnetic anisotropy, with a significant out-of-plane magnetization, for sample A, while an in-plane biaxial magnetic anisotropy with in-plane < 100 > as easy axes was evidenced for sample B. PNR magnetization reversal experiments showed the occurrence of a spin-flip maximum upon magnetization reversal only for sample B. A mechanism of magnetization reversal proceeding by 180 degrees domain-wall nucleation and propagation is proposed for sample A, while an incoherent rotation mechanism by 90 degrees domains is proposed for sample B. The reversal mechanism is shown to be correlated to the anisotropy of the samples which depends on the T/T-c ratio. (c) 2005 American Institute of Physics.