Magnetic Behaviour of Disordered Ising Ferrimagnet in High Magnetic Field

TL;DR

This paper presents a theoretical study of the magnetic behavior of disordered Ising ferrimagnetic systems under high magnetic fields, revealing field-induced magnetization reversal and its dependence on system parameters.

Contribution

It introduces a theoretical model using the cluster-variational method to analyze high-field magnetization behavior in disordered ferrimagnets, including magnetization reversal phenomena.

Findings

Magnetization vanishes at the Curie temperature in ferrimagnetic state.

Field-induced reversal of magnetization occurs at a switching temperature below TC.

Maximum magnetization increases with the applied magnetic field.

Abstract

The magnetic behaviour of a disordered ferrimagnetic system Ap B1-p where both A and B represent the magnetic atoms with respective spin SA = 1/2 and SB = 1 in presence of high magnetic field is treated theoretically.Assuming the magnetic interaction can be described through Ising Hamiltonian the approximate free energy is obtained using the cluster-variational method. The field dependence of the magnetization is then obtained for different concentration p and exchange parameters (JAA, JBB and JAB). For p = 0.5,the magnetization M in ferrimagnetic state and in absence of compensation temperature Tcm vanishes at TC.Field induced reversal of M is found at switching temperature TS (<TC) which is decreasing function of field H.A maximum in M is found above TS and the maximum value of M increases with field.In ferrimagnetic state M increases almost linearly at high H region. For system with large ferromagnetic JAA,the compensation temperature Tcm is increasing function of JBB and JAB .The decrease in compensation temperature is linear at small field and tends to saturate at higher field.The sharpness of the magnetization reversal is increased with H.For fully compensated state of the system with p = 2/3,the magnetization in presence of H also exhibits switching behaviour at TS .For p = 0.2 the field induced reversal of magnetization occurs more sharply.The orientational switching of the sublattice magnetization MA and MB with field increases the Zeeman energy and is the origin of magnetization reversal at Ts