Effect of Crystal-Field Anisotropy on Irreversible Phenomena in Spin-Glasses

We study the angular dependence of the field-cooled susceptibility ${\chi }_{\mathrm{eq}}$ of ${\mathrm{Fe}}_2$Ti${\mathrm{O}}_5$, a spin-glass with a strong uniaxial anisotropy, by rotating the measuring field $\overrightarrow{\mathrm{H}}$ with respect to the cooling field ${\overrightarrow{\mathrm{H}}}_c$. Unlike the behavior found in classical spin-glasses (i) the anisotropy in ${\chi }_{\mathrm{eq}}$ depends on the direction of ${\overrightarrow{\mathrm{H}}}_c$ and (ii) the irreversible magnetization does not rotate with $\overrightarrow{\mathrm{H}}$. The de Almeida-Thouless line is identified via the field and temperature dependence of the anisotropy in ${\chi }_{\mathrm{eq}}$.