Electronic structure and magnetic properties of GdxLa1-xNi5 system

Magnetic measurements were performed on GdxLa1-xNi5 compounds in the temperature range 1.7-300 K and fields up to 90 kOe. There is a transition from a spin fluctuation behaviour, characteristic for LaNi5, to a ferrimagnetic type ordering for x >= 0.2. The critical field for appearance of induced Ni moment was estimated. Then, the nickel moments, at 1.7 K, increase linearly with the exchange field. Band structure calculations were performed on RNi5 and GdxLa1-xNi5 systems. The Gd 5d band polarization is due to both local 4f-5d exchange and 5d-3d short range interactions with neighbouring atoms. There are also 5d-5d interactions through orbitals having lobes oriented along the c-axis. The differences between magnetic moments at 2c and 3g sites, obtained from band structure calculations, were correlated with their local environments. The mean effective nickel moments decrease when increasing gadolinium content, an opposite behaviour to that evidenced for ordered Ni moments at 1.7 K. This behaviour was attributed to gradual quenching of spin fluctuations by internal field.