Investigations of SrRuO3 and Sr2RuO4

The structural and magnetic properties of perovskites SrRuO3, CaRuO3. Sr(1-x)CaxRuO3 (x=0.5, 0.75) and the layered perovskite Sr2Ru04 have been investigated using X-ray diffraction, neutron scattering and SQUID measurements. SrRuO3 is ferromagnetic with a transition temperature of Tc=162K. It remains orthorhombic up to 450K. CaRuO3 is paramagnetic down to 2K and shows no structural phase transition between 2K and 300K. Sr2RuO4 is neither magnetically ordered nor does it change its crystallographic structure between 2K and 450K. The nature of the magnetism in SrRuO3 has been found to originate from itinerant 4d band electrons. CaRuO3 possesses a narrower 4d band compared to SrRuO3. The width of the 4d band in CaRuO3 does not allow any magnetic order. The unit cell differences between SrRuO3 and CaRuO3 are also due to the band structure. Paramagnetic neutron scattering also supports the notion of itinerant 4d band magnetism in these ruthenates.