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

Abstract The magnetization of the systems, K 2 Fe 1− x In x Cl 5 · H 2 O, Rb 2 Fe 1− x In x Cl 5 · H 2 O and Mn 1− x Zn x F 2 , is studied in low magnetic fields applied along the easy axis ( H axial M r always appears below the Neel temperature T N when cooling in a fixed axial field H axial > 10 −3 Oe. M r increases with decreasing T . At a fixed T , M r increases with H axial , but M r is practically saturated in fields as low as ∼ 1 Oe. The normalized remanent magnetization is a universal function of the reduced temperature t = T / T N . This function is: 1) independent of H axial 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 β r , which describes the T -dependence of M r , is between 0.35 and 0.4.