Magnetic specific heat and critical magnetic susceptibility of the diluted antiferromagnet CopMg1−pO

Abstract

For CopMg1−pO, a prototype randomly diluted fcc antiferromagnet, measurements of the specific heat versus temperature show that the size of the λ anomaly at TN decreases as p decreases. These results show that with increasing dilution, a progressively larger fraction of the magnetic entropy is removed by short-range order processes. The critical susceptibility χc at TN increases as p decreases, supporting the idea that near Mg sites, the balance of the two antiferromagnetic sublattices is destroyed. After correcting for single ion contribution, χc(p)/χc(1) is found to vary as (p−pc)−τ for p<0.47 (pc=0.136). The experimental value of τ≊0.7 is in reasonable agreement with the numerical estimate of τ=0.5±0.2 by Harris et al. for cubic systems.