Ferromagnetism in UCo1−xMnxAl and UCo1−xVxAl

Abstract

UCoAl is an itinerant 5f-electron metamagnet with a tiny critical field of transition Bc≈0.4 T (at 1.3 K). Critical magnetic parameters of this material are strongly sensitive to chemical environment of U atoms. We present results of a pilot study of formation, crystal structure and magnetism of UCo1−xTxAl compounds for T=Mn and V, x≤0.1. All these compounds have been found to be isostructural with the parent compound. Already for x=0.01 in both systems a spontaneous magnetization Ms has been observed at low temperatures. Anomalies in the AC susceptibility as a function of temperature point to Tc≈28 and 25 K respectively for Mn and V doping. The ferromagnetism induced in UCo1−xTxAl compounds due to a substitution of light transition metal for Co is discussed within a model considering effects of varying 5f-ligand hybridization on the stability of U 5f-moment and on exchange interactions.