Spectroscopic study of the field-induced spin reorientation in ErCrO3

Using the optical Zeeman absorption spectrum of ${\mathrm{Er}}^{3+}$ and ${\mathrm{Cr}}^{3+}$ in ErCr${\mathrm{O}}_3$, the field-induced spin reorientations between ${\Gamma }_1$, ${\Gamma }_2$, and ${\Gamma }_4$ phases are investigated extensively. The data are analyzed using a two-sublattice molecular-field model. It is concluded that not only the antisymmetric exchange interactions between ${\mathrm{Cr}}^{3+}$ and ${\mathrm{Er}}^{3+}$ ions, but also the anisotropic symmetric ones are responsible for the spin reorientation. Comparing the ground-doublet splitting of the ${\mathrm{Er}}^{3+}$ ion between the ${\Gamma }_1$, ${\Gamma }_4$, and ${\Gamma }_2$ phases, the anisotropic symmetric part is separable from the predominant antisymmetric part. The anisotropic-symmetric to the antisymmetric-part rate is about 0.33.