Low-field remanent magnetization in site-diluted easy-axis antiferromagnets. A universal behavior

Abstract

The magnetization of the systems, K2Fe1−xInxCl5 · H2O, Rb2Fe1−xInxCl5 · H2O and Mn1−xZnxF2, is studied in low magnetic fields applied along the easy axis (Haxial < 10 Oe). A remanent magnetization Mr always appears below the Néel temperature TN when cooling in a fixed axial field Haxial > 10−3 Oe. Mr increases with decreasing T. At a fixed T, Mr increases with Haxial, but Mr is practically saturated in fields as low as ∼ 1 Oe. The normalized remanent magnetization is a universal function of the reduced temperature t = T/TN. This function is: 1) independent of Haxial for a given sample, 2) independent of x for a given system, and 3) the same for the three site-diluted systems. The effective critical exponent βr, which describes the T-dependence of Mr, is between 0.35 and 0.4.