Electronic phase separation in transition metal oxide systems

Abstract

Electronic phase separation is increasingly getting recognized as a phenomenon of importance in understanding the magnetic and electron transport properties of transition metal oxides. The phenomenon dominates the rare-earth manganates of the formula Ln(1-x)A(x)MnO(3) (Ln = rare earth and A = alkaline earth) which exhibit ferromagnetism and metallicity as well as charge-ordering, depending on the composition, size of A-site cations and external factors such as magnetic and electric fields. We discuss typical phase separation scenarios in the manganates, with particular reference to Pr1-xCaxMnO3 (x = 0.3-0.4), (La(1-x)Ln(x))(0.7)Ca0.3MnO3 (Ln = Pr, Nd, Gd and Y) and Nd0.5Sr0.5MnO3. Besides discussing the magnetic and electron transport properties, we discuss electric field effects. Rare-earth cobaltates of the type Pr0.7Ca0.3CoO3 and Gd0.5Ba0.5CoO3 also exhibit interesting magnetic and electron transport properties which can be understood in terms of phase separation.