Exchange bias and magnetic memory effect in CuMn2O4

Abstract

We observe exchange bias (EB) and magnetic memory effect in spinel CuMn${}_2$O${}_4$. A significant EB field of approximately 700 Oe is observed at 3 K under a cooling field of 15 kOe. This effect decreases sharply with increasing temperature and nearly vanishes above 12 K. Analysis of the cooling field dependence of the EB at 3 K indicates a cluster size of approximately 53 nm. Clear signatures of the magnetic memory effect, as revealed by dc magnetization measurements, suggest a glassy magnetic state at low temperatures, consistent with a cluster-glass state. In addition to the multiple super-exchange interactions involving Cu${}^{+}$/Cu${}^{2+}$ and Mn${}^{3+}$/Mn${}^{+}$ ions, the strong Jahn-Teller effect in tetrahedrally coordinated Cu${}^{2+}$ and octahedrally coordinated high-spin Mn${}^{3+}$ ions introduces considerable disorder, supporting the presence of a glassy magnetic state in CuMn${}_2$O${}_4$.