Ground-state phase diagrams of Ising metamagnet in a mixed longitudinal and transverse magnetic field

Abstract

The ground-state magnetic properties of a two-sublattice Ising metamagnet in a mixed longitudinal and transverse magnetic field are studied within the effective-field theory. A parameter j 2= J 2/ J 1 is introduced, which reflects the strength ratio of spin coupling between adjacent planes and in each plane. In addition to the second-order transition lines, the first-order transition lines are also presented, since the ground-state energy can be calculated numerically. The ground-state phase diagrams in h x – h z are presented. The results show that when j 2<0 the phase transition of the system is always first-order for h x <2.751, and when −1000⩽ j 2<0 it is always second-order for h x >4.36. For the given h x (0< h x <14.71), the longitudinal critical magnetic field increases as j 2 decreases. The reentrant phenomenon occurs in the range of j 2<−11.89, h x >14.71. There is no fourth-order critical point in the phase diagrams given by using EFT as found by using mean field theory (MFT).