Spin saturation of the random antiferromagnet (Cd,Mn)Te in magnetic fields to 150 T

Spin alignment of magnetic ${\mathrm{Mn}}^{2+}$ ions in the random antiferromagnet ${\mathrm{Cd}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Mn}}_{\mathit{x}}$Te is studied in high magnetic fields. Faraday-rotation measurements at T∼10 K were made up to 150 T for magnetic concentrations ranging from x=0.1 to 0.6. For x=0.1 and 0.2 the applied fields are large enough to overcome the internal antiferromagnetic exchange fields, leading to total spin saturation, 〈${\mathit{S}}_{\mathit{Z}}$〉=5/2, at B=80 and 130 T, respectively. For higher concentrations the spin alignment becomes increasingly difficult due to the increasing number of neighboring spins. A mean-field model that takes into account the random site occupation self-consistently fits the measured field and concentration dependencies of 〈${\mathit{S}}_{\mathit{Z}}$〉 remarkably well.