Three-dimensional magnetic ordering in the Rb₂CuCl₄layer perovskite—structural correlations

Abstract

This work investigates the magnetic structure of Rb2CuCl4 as a function of pressure and temperature using neutron diffraction. As in most A2CuCl4 layered perovskites, there is a 2D ferromagnetic order within the layers. This behaviour is due to the Jahn–Teller (JT) antiferrodistortive structure of the CuCl6 units. Rb2CuCl4 undergoes a 3D magnetic transition at TN = 16 K, which mainly depends on the weak antiferromagnetic interlayer interaction. The pressure slightly increases TN, as ∂TN/ ∂ P = 0.13 K kbar−1. This behaviour is interpreted in terms of pressure-induced tilts and reduction of interlayer distance, both effects increasing the antiferromagnetic exchange coupling between layers. The results are compared with previous magnetic studies under chemical and hydrostatic pressure along layered perovskites series of [CnH2n+1NH3]2CuCl4 (n = 1–3) and BMnF4 (B = Li, Na, K, Rb, Tl, Cs and NH4) involving JT ions of Cu2+ and Mn3+, respectively. We show that the ratio of the interlayer to intralayer coupling, and thus the nature of the magnetic order, can be tuned by chemical or hydrostatic pressure along the A2CuCl4 series. The present findings stress the relevance of octahedral tilts on the magnetic behaviour of layered perovskites.