Reentrant spin-glass behaviour in highly frustrated Mn-rich spinel zinc manganate

Abstract

The present work offers an insight into the magnetic properties of Mn-rich spinel zinc manganate. Rietveld refinement reveals the formation of Zn 0.67 Mn 2.33 O 4, where Zn 2+ and Mn 2+ ions are randomly distributed in the tetrahedral sublattice. DC and AC susceptibility measurement of Zn 0.67 Mn 2.33 O 4 infers the occurrence of two kinds of transition below 11 K. Paramagnetic to ferrimagnetic transition occur at 10.7 K and ferrimagnetic to spin glass-like transition occurs at 5.8 K. The long-range canted ferrimagnetic ordering is corroborated using modified Lotgering model and calculated the exchange interaction values (J AA = 5.2 K, J AB = 5.3 K, J BB = 14.8 K). Further, the observed shift in freezing temperature with DC magnetic field obeys Almeida-Thouless behaviour and frequency dependence of AC susceptibility follows Vogel-Fulcher law. However, the complete establishment of the canonical spin glass state is denied since the manganese ions occupied at the tetrahedral site is equal to the percolation threshold (=33%). Subsequently, the observed spin glass-like behaviour (5.8 K) below Curie temperature (10.7 K) evidences the reentrant spin glass nature. Similarly, the strong frustration in Zn 0.67 Mn 2.33 O 4 lattice is observed through the substantial negative value of Curie-Weiss temperature (∼−599 K) and very high frustration factor ( f = 56). Overall, the chosen Zn 0.67 Mn 2.33 O 4 is a highly frustrated magnetic system revealing re-entrant spin-glass behaviour.