Staggered moment dependence on field-tuned quantum fluctuations in 2D frustrated antiferromagnets

TL;DR

This paper introduces a new method combining exact diagonalization and spin wave analysis to determine the frustration ratio in 2D antiferromagnets, providing insights into quantum fluctuations and magnetic properties.

Contribution

It presents an efficient criterion to identify the frustration ratio J_2/J_1 in quasi-2D antiferromagnets based on field-dependent staggered moments.

Findings

Determined J_2/J_1 ~ 0.2 for Cu(pz)_2(ClO_4)_2

Revealed non-monotonic field dependence of staggered moments

Explained anomalous transition temperature increase in magnetic fields

Abstract

We propose an efficient method to identify the degree of frustration in quasi-2D antiferromagnets described by the J_1-J_2 Heisenberg model. The frustration ratio J_2/J_1 is usually obtained from analysis of susceptibility, specific heat and saturation field. We show that the non-monotonic field dependence of the staggered moment caused by the suppression of quantum fluctuations in a field depends strongly on the frustration ratio. This gives a powerful criterion to determine J_2/J_1 using a combination of exact diagonalization (ED) method for finite clusters and spin wave analysis. We apply this method to the quasi-2D compound Cu(pz)_2(ClO_4)_2 and show that it leads to an intermediate ratio J_2/J_1 ~ 0.2 for the frustration. We also explain the observed anomalous increase of transition temperature in applied fields as an effect of reduced quantum fluctuations.