Ferromagnetic resonance study of the free-hole contribution to magnetization and magnetic anisotropy in modulation-doped Ga_(1-x)Mn_xAs/Ga_(1-y)Al_yAs:Be

摘要

Ferromagnetic resonance (FMR) is used to study magnetic anisotropy of GaMnAs in a series of Ga_(1-x)Mn_xAs/Ga_(1-y)Al_yAs 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 Ga_(1-x)Mn_xAs layers—also leads to a very significant increase of their uniaxial anisotropy field. The FMR measurements further show that the effective g-factor of Ga_(1-x)Mn_xAs 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 Ga_(1-x)Mn_xAs system as a whole.