A low field technique for measuring magnetic and magneto-resistance anisotropy coefficients applied to (Ga,Mn)As

We demonstrate a simple, low cost, magneto-transport method for rapidly characterizing the magnetic anisotropy and anisotropic magneto-resistance (AMR) of ferromagnetic devices with uniaxial magnetic anisotropy. This transport technique is the analogue of magnetic susceptibility measurements of bulk material but is applicable to very small samples with low total moment. The technique is used to characterize devices fabricated from the dilute magnetic semiconductor (Ga,Mn)As. The technique allows us to probe the behavior of the parameters close to the Curie temperature, in the limit of the applied magnetic field tending to zero. This avoids the complications arising from the presence of paramagnetism.