Structure-controlled magnetic anisotropy in ferromagnetic semiconductor superlattices

We present experimental studies of the in-plane magnetic anisotropy of ferromagnetic semiconductor superlattices. The samples have half-monolayer MnAs planes that alternate with GaAs spacers of thickness t = 28, 42, and 56 A. For the lowest-t samples, planar Hall effect and magnetization data indicate domain-wall-mediated magnetic switching between predominantly cubic easy axes, while samples with larger t exhibit uniaxial anisotropy. The data demonstrate that the structure of ferromagnetic semiconductor superlattices controls their magnetic anisotropy.