Opposing spin-canting mechanism in single-crystal LuVO3 and YVO3

A canted-spin ferromagnetic moment M parallel to the orthorhombic (Pbnm) a axis of a YVO3 single crystal changes sign from the direction of a measuring field H≤1kOe on warming from 5K across a first-order orbital-spin reordering temperature TCG; the magnetization changes sign again on warming across T* in the interval TCG<T*<TN, where TN is the antiferromagnetic Néel temperature. Although the magnitude of M and its sign changes are the same for a sample cooled in a measuring field (FC) and zero-applied field (ZFC) to 5K, the M(T) curves differ for warming after FC and ZFC to just above TCG; but the sign reversal of M occurs at the same T* with the same measuring field H. These unusual features are argued to be the result of two coupled spin-canting mechanisms that oppose one another, an antisymmetric exchange operating on a c-axis spin component, and a 90° site anisotropy in the a-b plane operating on a b-axis component of the spin. The relative strength of the antisymmetric exchange increases with decreasing V OV bond angle to give a T* close to a TOO TN in LaVO3 and no T* above TCG in LuVO3.