A single-crystal compensated ferrimagnet ${\mathrm{Ni}}_4{\mathrm{Nb}}_2{\mathrm{O}}_9$, consisting of two antiferromagnetically coupled ferromagnetic (FM) $\mathrm{N}{\mathrm{i}}^{2+}$ layers with opposite moments in the ab plane, exhibiting noninterface exchange bias (EB), was investigated. The magnetization hysteresis loops $M\left(\theta \right)$, measured at a weak field H rotating in FM layers clockwise and then counterclockwise, show two successive M flips in opposite directions with a large hysteresis of the flip angle ${\theta }_{\mathrm{MR}}$. It was found that the angle ${\theta }_{\mathrm{MR}}$ shifts due to EB to higher or lower values, depending on the sign of the unidirectional anisotropy EB specified by the field cooling protocol. Furthermore, the EB effect also influences the temperature of spontaneous switching $T_{\mathrm{sw}}$ from negative to positive magnetization, which occurs below $T_{\mathrm{comp}}=33\mathrm{K}$, at a constant field H. Namely, $T_{\mathrm{sw}}$ decreases in the presence of positive unidirectional anisotropy and increases in the presence of negative anisotropy, indicating that the energy required to flip M depends on the sign of EB. The features discovered allow us to more fully comprehend the nature of the EB effect in coupled FM layers of compensated ${\mathrm{Ni}}_4{\mathrm{Nb}}_2{\mathrm{O}}_9$ ferrimagnet.

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• Antiferromagnetism
• Exchange bias
• Magnetic anisotropy