Magnetic properties of rare-earth magnesium compounds of the type RMg2

Abstract

The magnetic and crystallographic properties of rare earth compounds of the type RMg₂ were studied. The compounds in which R represents La, Ce, Pr, Nd, Sm and Gd were found to be of the cubic Laves phase structure. The remainder of compounds of this series crystallize in the hexagonal Laves phase structure. For all compounds the lattice constants were determined. Most of these compounds order ferromagnetically at temperatures well below 100 K. Exceptions are LaMg₂, YbMg₂ and YMg₂ which exhibit Pauli paramagnetism, whereas SmMg₂ and EuMg₂ order antiferromagnetically. From the magnetic properties and from the lattice constants it is concluded that Eu and Yb are both divalent in these compounds. A peculiar temperature dependence of the magnetization was observed in SmMg₂. A sharp peak‐like rise in the magnetization occurs within a temperature range of 10 K only, the magnetization being nearly temperature‐independent otherwise. Details regarding the nature of the crystal fields in the cubic RMg₂ compounds were derived from specific heat measurement performed on LaMg₂, CeMg₂ in the temperature range 1.5–40 K.