Features of the magnetization of an antiferromagnet with single-ion anisotropy of the easy-plane type and with ion spins S=1

Abstract

A theory is proposed for the two-step phase transition from the singlet to a ferromagnetic state in systems of the ABX3 type. It is shown that the transition is due to a substantial rearrangement of the single-ion spectrum. The critical fields and magnetic susceptibility are calculated.

Dynamic and static properties of rigidly fixed ultrathin ferromagnetic films with S = 1 and competing anisotropies

“…As before, the soft mode in this phase state will be the quasimagnon branch (38). For an arbitrary orientation of the wave vector, Eq.…”

“…(38) is the low-frequency branch, which we analyze below. The quasiphonons in the quadrupole phase do not interact with the magnetic subsystem; in the neighborhood of the phase transition their spectra continue to be linear in the wave vector and the sound speed is unchanged.…”

“…These effects have been reviewed in some detail 31 and studied in a number of papers on highly anisotropic ferroand antiferromagnetic materials. [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49] One such effect is the appearance of a quadrupole phase in magnets with a large single-ion anisotropy. As noted long ago, 46 the inclusion of even a small single-ion anisotropy leads to a change in the modulus of the magnetization with length, which, in turn, requires going beyond the simplest of phenomenological approaches.…”

Effect of tilted anisotropy on spin states of strongly anisotropic 2D film

“…In this paper, we consider an interesting class of magnetic systems that possess a giant easy plane sin gle ion anisotropy β zz , which is comparable with or even exceeds the exchange interaction J 0 . The exist ence of this anisotropy in the system leads to a number of interesting effects of purely quantum nature, which cannot be explained by using phenomenological mod els [9][10][11][12][13][14][15]. Among these effects, we can single out the formation of so called quadrupole phases character ized by a long range magnetic order not of the vector type (the magnetization of the system is zero), but of the tensor type [15].…”

Quantum phase transition: Van Vleck antiferromagnet in a magnetic field

“…The same calculations should also be made for spin quadrupole moment. As reported in references [38,39], solution of the problem of spin configuration in the magnetic field suggests minimization of expression (6) by all available unknown quantities: the geometric angle θ and (see equation (4)) the angle φ of quantum states mixture. This method of finding the observables, being completely an equivalent to the solution of quantum self-consistent problem, is more convenient and more consistent, because it allows to perform generalization on the case of finite temperatures [27,28].…”