We report a systematic investigation of ac magnetic susceptibility in (Ga,Mn)As films as a function of temperature and magnetic field, carried out in parallel with dc magnetization measurements. The temperature dependence of ac susceptibility χac shows anisotropic behavior: 1) a single peak in χac is observed close to TC for the  orientation of the driving ac field; 2) a single peak is also seen close to 22 K for the field along ; and 3) peaks at both these temperatures are observed for the field applied along . A detailed analysis of the ac and dc data unambiguously indicates that the peak near TC is related to the paramagnetic-to-ferromagnetic phase transition, with the ferromagnetic domains nucleating with their easy axes aligned with the  direction, providing a clear picture of uniaxial domain behavior near TC. The peak near 22 K, on the other hand, is related to the onset of biaxial domain structure in (Ga,Mn)As induced by the competition between uniaxial and cubic anisotropy. More specifically, the ac susceptibility peak near TC involves 180° magnetization flips along the  easy axis of the domains, while the peak near 22 K originates from magnetization wobbling between two biaxial easy axes separated by a small angle.
- Ferromagnetic semiconductors
- magnetic anisotropy
- magnetic domains and magnetic susceptibility
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering