Crossover from pure Ising to random exchange dominated behavior of the two-dimensional antiferromagnet Rb2Co1-xMgxF4

TL;DR

This study investigates how the magnetic susceptibility of a two-dimensional antiferromagnet changes from pure Ising behavior to random exchange dominance as disorder increases, providing a comprehensive quantitative analysis across different impurity levels.

Contribution

It offers the first detailed quantitative analysis of susceptibility behavior across the crossover from pure Ising to random exchange dominated regimes in a 2D antiferromagnet.

Findings

Susceptibility data aligns with theoretical models considering both energetic and random contributions.

The crossover behavior is characterized across the Griffiths regime.

A unified description of susceptibility for various impurity levels is achieved.

Abstract

The temperature dependence of the uniform susceptibility, chi, of diluted two-dimensional Ising antiferromagnets Rb2Co1-xMgxF4,0<=x<=0.4, is investigated in the limit of vanishing external field. Novel data for x = 0.15 are compared with those obtained for x = 0 and 0.4 by Breed et al. (1969) and Ikeda (1983), respectively. Whereas in the pure case, x = 0, Fishers (1962) "energetic contribution" dominates, Aharony et al.s (1979,1986) "random contribution" becomes increasingly important with increasing x. Taking into account both terms not only with respect to the global ordering temperature, TN(x), but also in relation to the "local" phase transition temperatures TN throughout the Griffiths regime,TN(x)<=TN<=TN(0), a satisfactory quantitative description of chi vs. T is deduced for any x above the percolation threshold.