Results of self-consistent band calculations are reported for the C15 structured XAl2 materials (X = Y, La, and Ce) using the local spin density functional formalism for assumed ferromagnetic and antiferromagnetic states as well as the paramagnetic state. The X-atoms are found to be the dominant factor is determining the electronic structure near the Fermi energy and this is enhanced by the presence of f-bands close to (LaAl2) or at (CeAl2) the Fermi energy. In paramagnetic CeAl2, the f-bands are about 1 eV wide and, although principally above the Fermi energy, extend down to accomodate the additional electron compared to LaAl2. The ferromagnetic state is found not to be stable. By contrast, the antiferromagnetic state is found to be stable with a magnetic moment of 0.88μB per Ce atom in very good agreement with the maximum moment, 0.89μB found in the neutron measurements of Barbara et al. A significant narrowing of the f-bandwidth is observed in the antiferromagnetic state. The antiferromagnetic spin density ordering appears to be related to nesting features in this underlying Fermi surface in LaAl2 (i.e., no 4f electron) rather than that of CeAl2.
ASJC Scopus subject areas
- Condensed Matter Physics