Transverse ordering in anisotropic spin glasses

The low-field susceptibility along the easy axis of the spin glass ${\mathrm{Fe}}_2$ ${\mathrm{TiO}}_5$ exhibits a sharp cusp at $T_g$=48 K, whereas the susceptibility in transverse directions exhibits a broad maximum around 6 K. In all directions irreversibility appears already below $T_g$. Transverse irreversibility, however, is weaker by an order of magnitude than the longitudinal one. This behavior is discussed in terms of a model of a spin glass which has a weak random anisotropy in addition to a uniform easy axis.