Quantum analogue of the spin-flop transition for a spin pair

TL;DR

This paper investigates quantum magnetization steps in a spin pair with antiferromagnetic coupling, analyzing how anisotropy influences the step-like magnetization curves through both analytical and numerical methods.

Contribution

It introduces a comprehensive analysis of quantum magnetization jumps in spin pairs, highlighting the effects of anisotropy origin and spin magnitude on the magnetization behavior.

Findings

Magnetization curves can show jumps greater than one unit depending on anisotropy.

The behavior varies from quasiclassical to quantum as spin S increases.

Parameter regions where quantum effects dominate are identified.

Abstract

Quantum (step-like) magnetization curves are studies for a spin pair with antiferromagnetic coupling in the presence of a magnetic field parallel to the easy axis of the magnetic anisotropy. The consideration is done both analytically and numerically for a wide range of the anisotropy constants and spins up to $S \gtrsim 100$. Depending on the origin of the anisotropy (exchange or single-ion), the magnetization curve can demonstrate the jumps more than unity and the concentration of the unit jumps in a narrow range of the field. We also point the region of the problem parameters, where the behavior is quasiclassical for $S = 5$, and where system is substantially quantum in the limit $S \to \infty$.