Electronic and magnetic properties of CeCoGa

Abstract

We report the magnetic and electronic transport properties of CeCoGa, using magnetic susceptibility, magnetization, specific heat and electrical resistivity investigations. We also present X-ray photoemission valence band spectra (VB-XPS) as well as ab-initio band structure calculations for the ferromagnetic and antiferromagnetic ordering. The dc and ac magnetic susceptibility data reveal a magnetic phase transition at TN = 4.3 K. For T < TN magnetization M vs. magnetic field B isoterms have two metamagnetic transitions. Above TN susceptibility shows evidence of spin-glass like behavior. The magnetic entropy is strongly reduced at TN due to the on-site Kondo coupling. For CeCoGa the Kondo temperature is ∼20 K, much larger than the temperature of the magnetic ordering. Our calculations show that within bare local spin density approximation (LSDA) the ground state of CeCoGa is weakly magnetic, however, the 4f correlations when they are included within LSDA + U approach lead to stable antiferromagnetic ground state. Calculations for moderate U parameter indicate that magnetic ordering is present not only at the Ce sublattice, but also for the Co sites, moreover small induced magnetic moment is also present at the Ga sites. All sublattices exhibit antiferromagnetic ordering with different values of local magnetic moments what explains the ferrimagnetic behavior of CeCoGa. The magnetization M vs. magnetic field B shows at T = 2 K two metamagnetic features at B = 0.1 T and B = 5 T, which well correlates with the calculated magnetic moments of Co and Ga. The first transition can be attributed to spin–flop within the magnetic moments induced in Ga sublattice, whereas the anomaly at B = 5 T is related to the spin–flop within the Co sublattice.