Formation of metastable cubic phase in Ce100−xAlx (x=45, 50) alloys and their thermal and magnetic properties

Abstract

Ce100−xAlx (x=45 and 50) alloys were synthesized by rapid quenching technique in the form of ribbons composed of nanocrystalline phase of CeAl with the ClCs-type structure (Pm-3m space group) embedded in an amorphous matrix. The cubic CeAl phase is known as metastable with random distribution of Ce and Al atoms in the unit cell. The crystalline volume fraction is about 7.5% in Ce55Al45 and 3% in Ce50Al50. The alloy Ce55Al45 shows better thermal stability than Ce50Al50, indicated by higher effective activation energy and higher crystallization temperature. Small off-stoichiometry in Ce55Al45 results in degrading the glass forming ability and promotes formation of the cubic CeAl phase, as confirmed by magnetic measurements. In both alloys, the Ce ions are in stable trivalent state and order magnetically near 20K. Another magnetic phase transition close to 10K was found for Ce50Al50 and was attributed to the presence of the well-known stable orthorhombic CeAl phase. To the best of our knowledge, the magnetic behavior of the CeAl cubic phase is reported here for the first time.