Correlation among disorder, electronic and magnetic phases of SrRuO3

Electric and magnetic properties of Sr1-xBaxRu1-xTixO3 (0 <= x <= 0.8) have been investigated to find the interrelationship between metallicity and ferromagnetism in SrRuO3 (SRO). The simultaneous doping of Sr and Ru with Ba and Ti results in single phase SRO at x = 0.1 and mixed phase of SRO and hexagonal BaTiO3 (h-BTO) at x >= 0.2. Co-doping at Sr and Ru sites gives rise to oxygen vacancy and mixed valency of Ru (Ru3+ and Ru4+). Room temperature resistivity increases due to modification of p(O)-d(Ru) hybridization and phase segregation. Temperature dependent resistivity reveals metal-insulator transition around 232K at x = 0.1 and insulator down to 2K at x >= 0.2. The insulating state (x = 0.1) at low temperature is well described by weak localization and electron-electron interaction. Temperature dependence of resistivity (x >= 0.2) follows Mott's three dimensional variable range hopping model. Localization length and average hopping distance decrease with the increase of x, indicating the presence of more disorder. Ferromagnetic transition temperature decreases to 149K at x = 0.1 and remains constant up to x = 0.5. The Curie-Wiess (CW) temperature (Theta CW) decreases monotonically and becomes negative at x = 0.5. The effective magnetic moment estimated from CW law is smaller than that of pure SRO due to the formation of Ru3+ ions. The saturation magnetization diminishes, suggesting the demagnetization factor owing to diamagnetic h-BTO. The coercivity increases from 6700 Oe (x = 0) to 12 500 Oe (x = 0.4) and then decreases to 3700 Oe (x = 0.5). Ferromagnetic cluster comprising of doped SRO gives rise to the formation of a Griffith-like phase. The co-occurrence of high jump in resistivity ratio and disappearance of ferromagnetism suggests an interplay between transport process and magnetism at low temperature.