Ferromagnetic resonance study of the free-hole contribution to magnetization and magnetic anisotropy in modulation-doped Ga1-xMnxAs/Ga1-yAlyAs:Be -: art. no. 035307

Ferromagnetic resonance (FMR) is used to study magnetic anisotropy of GaMnAs in a series of Ga1-xMnxAs/Ga1-yAlyAs heterostructures modulation-doped by Be. The FMR experiments provide a direct measure of cubic and uniaxial magnetic anisotropy fields and their dependence on the doping level. It is found that the increase in doping-in addition to raising the Curie temperature of the Ga1-xMnxAs layers-also leads to a very significant increase of their uniaxial anisotropy field. The FMR measurements further show that the effective g-factor of Ga1-xMnxAs is also strongly affected by the doping. This in turn provides a direct measure of the contribution from the free hole magnetization to the magnetization of the Ga1-xMnxAs system as a whole.