One Dimensional(1D)-to-2D Crossover of Spin Correlations in the 3D Magnet ZnMn2O4

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

The present work offers an insight into the magnetic properties of Mn-rich spinel zinc manganate. Rietveld refinement reveals the formation of Zn_0.67Mn_2.33O_4, where Zn²⁺ and Mn²⁺ ions are randomly distributed in the tetrahedral sublattice. DC and AC susceptibility measurement of Zn_0.67Mn_2.33O₄ 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_0.67Mn_2.33O₄ 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_0.67Mn_2.33O₄ is a highly frustrated magnetic system revealing re-entrant spin-glass behaviour.

Sub-lattice of Jahn-Teller centers in hexaferrite crystal

A novel type of sub-lattice of the Jahn-Teller (JT) centers was arranged in Ti-doped barium hexaferrite BaFe₁₂O₁₉. In the un-doped crystal all iron ions, sitting in five different crystallographic positions, are Fe³⁺ in the high-spin configuration (S = 5/2) and have a non-degenerate ground state. We show that the electron-donor Ti substitution converts the ions to Fe²⁺ predominantly in tetrahedral coordination, resulting in doubly-degenerate states subject to the [Formula: see text] problem of the JT effect. The arranged JT complexes, Fe²⁺O₄, their adiabatic potential energy, non-linear and quantum dynamics, have been studied by means of ultrasound and terahertz-infrared spectroscopies. The JT complexes are sensitive to external stress and applied magnetic field. For that reason, the properties of the doped crystal can be controlled by the amount and state of the JT complexes.

ZnMn2O4 nanorods: an effective Fenton-like heterogeneous catalyst with t2g3eg1 electronic configuration

The t_2g³e_g¹ electron configuration of Mn benefits the Fenton-like spinel ZnMn₂O₄ nanorod catalyst by promoting the creation of oxygen-containing radicals.