Ferrimagnetism of MnV_2O_4 spinel

TL;DR

This paper develops a modified spin-wave theory to describe the ferrimagnetic behavior of MnV_2O_4, capturing the temperature-dependent magnetization and phase transitions observed experimentally.

Contribution

It introduces a new theoretical model that explains the complex magnon interactions and phase behavior in MnV_2O_4 ferrimagnet.

Findings

Reproduces the experimental ZFC magnetization curve.

Identifies two magnetic phases with distinct contributions from Mn and V ions.

Describes suppression of vanadium magnetic order at higher temperatures.

Abstract

The spinel MnV_2O_4 is a two-sublattice ferrimagnet, with site A occupied by the Mn^{2+} ion and site B by the V^{3+} ion. The magnon of the system, the transversal fluctuation of the total magnetization, is a complicated mixture of the sublattice A and B transversal magnetic fluctuations. As a result, the magnons' fluctuations suppress in a different way the manganese and vanadium magnetic orders and one obtains two phases. At low temperature (0,T^*) the magnetic orders of the Mn and V ions contribute to the magnetization of the system, while at the high temperature (T^*,T_N), the vanadium magnetic order is suppressed by magnon fluctuations, and only the manganese ions have non-zero spontaneous magnetization. A modified spin-wave theory is developed to describe the two phases and to calculate the magnetization as a function of temperature. The anomalous $M(T)$ curve reproduces the experimentally obtained ZFC magnetization.