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

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 j2=J2/J1 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 hx-hz are presented. The results show that when j2<0 the phase transition of the system is always first-order for hx<2.751, and when −1000⩽j2<0 it is always second-order for hx>4.36. For the given hx (014.71. There is no fourth-order critical point in the phase diagrams given by using EFT as found by using mean field theory (MFT).