A systematic study of magnetic order in divalent europium perovskites

The magnetic properties of a series of cubic perovskite materials, Eu(Al0.5Ta0.5)O3, Eu(Mg0.5W0.5)O3, and Eu(Lu0.5Ta0.5)O3 have been investigated using bulk magnetic and Mössbauer techniques. Eu(Al0.5Ta0.5)O3 is a ferromagnet (Tc ∼ 5°K, θc = + 8°K), Eu(Lu0.5Ta0.5)O3 is an antiferromagnet (TN = 4.0, θc = −8°K), while Eu(Mg0.5W0.5)O3 is probably antiferromagnetic (TN = 2.8°K, θc = − 1°K). These data are compared with the known properties of EuLiH3 and EuTiO3 and a sharp drop in θc as a function of increasing lattice constant is noted. A molecular field theory analysis of the data yields two possible sets of nn (J1) and nnn (J2) exchange constants for each compound which are compared with existing theories.