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 °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° domain-wall nucleation and propagation is proposed for sample A, while an incoherent rotation mechanism by 90° 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/Tc ratio. [ABSTRACT FROM AUTHOR]