Valence electron structures dependences of structural stability and properties of REX₃ (RE = rare earth; X = In, Tl) and RE(In, Co)₃ alloys

Abstract Intermetallic compounds RE In 3 ( RE = rare earth) have attracted much attention due to their unique characteristics: crystal field effect, Kondo effect, superconductivity, heavy fermion, and antiferromagnetism, and their cobalt diluted alloys exhibit the ferromagnetic half-metallic characteristics at room temperature. In this study, an empirical electron theory (EET) is employed to investigate systemically the valence electronic structure, the thermal and magnetic properties of REX 3 and their cobalt diluted alloys for revealing the mechanism of physical properties. The calculated bond length, melting point, and magnetic moment match the experimental ones very well. The study reveals that structural stability and physical properties of REX 3 and their cobalt dilute alloys are strongly related to their valence electron structures. It is suggested that the structural stability and cohesive energy depend upon the covalent electron, the melting point is modulated by covalent electron pair, and the magnetic moment is originated from 3d magnetic electron. The ferromagnetic characteristics of Co-diluted RE In 3 alloys is originated from the introduction of strong ferromagnetic Co atom, but, a competition is caused between the electron transition from valence electron to magnetic electron on d orbit and its reversal electron transformation with increasing the content of cobalt, which results in the formations of diluted magnetic Gd(In,Co) 3 alloy with minor amount of cobalt and strong magnetic Nd(In,Co) 3 alloy with doping more Co atoms.