Local control of magnetocrystalline anisotropy in (Ga,Mn)As microdevices: Demonstration in current-induced switching

The large saturation magnetization in conventional dense moment ferromagnets offers a flexible means of manipulating the ordered state through demagnetizing shape anisotropy fields, but these dipolar fields, in turn, limit the integrability of magnetic elements in information storage devices. We show that in a (Ga,Mn)As dilute-moment ferromagnet, with comparatively weaker magnetic dipole interactions, locally tunable magnetocrystalline anisotropy can take the role of the internal field which determines the magnetic configuration. Experiments and theoretical modeling are presented for lithographically patterned microchannels, and the phenomenon is attributed to lattice relaxations across the channels. The utility of locally controlled magnetic anisotropies is demonstrated in current-induced switching experiments. We report structure sensitive, current-induced in-plane magnetization switchings well below the Curie temperature at critical current densities similar to 10(5) A cm(-2). The observed phenomenology shows signatures of a contribution from domain-wall spin-transfer-torque effects.