Anomalous behavior of spin-glass CrMn alloys

Cr sub 1-x Mn sub x alloys and CrMn-based ternary spin-density-wave (SDW) alloys behave in many respects like the prototype spin glass (SG) CuMn, which also exhibits a SDW. However, in CuMn the magnetization M(H) is nonlinear up to H = 40 T, whereas in Cr sub 1-x Mn sub x with x < = 6.2% Mn, M(H) becomes linear by H approx = 0.3 T, with dM/dH independent of x like the peak temperature T sub m in the magnetic susceptibility chi (T). The explanation is that in CuMn the applied field H has to overcome the large randomly oriented local anisotropy fields responsible for the frustration of the Mn moments, whereas in CrMn the non-linearity at low H is due to frustration of the Cr moments by much weaker fields associated with SDW domains. Alloys Cr sub 1-x Mn sub x with x > = 13.5% exhibiting a strong Curie-Weiss paramagnetism in the SDW phase show a peak in dM/dH(H) like that seen in Fe-doped Cr alloys.