Strong unidirectional anisotropy in spin-density-wave (Cr+6.5%Co)1−xVx alloys

The magnetization, M(T), and magnetic susceptibility, χ(T) = M(T)/H, of the (Cr+6.5% Co)1−xVx (0⩽×⩽5% V) spin-density-wave (SDW) alloy system, have been measured in the presence of a magnetic field, H=100 Oe–5 T, in the field-cooled and zero field-cooled states, over the temperature range, 2⩽T⩽400 K. The thermal hysteresis corresponds to an irreversibility temperature Ti above the Néel temperature TN. M(H) measured at T=2 K in the FC (H=5 T) state exhibits magnetic hysteresis corresponding to a strong unidirectional anisotropy. The remanent magnetization MRem(T) decreases rapidly with increasing temperature, disappearing at Ti. The behavior is explained in terms of spin frustration of Cr moments close to the Co impurity atoms, with a component also due to Co clusters, whose moments are frozen in the SDW phase.