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−xA_xMnO₃ (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 Pr_1−xCa_xMnO₃ (x = 0.3–0.4), (La_1−xLn_x)_0.7Ca_0.3MnO₃ (Ln = Pr, Nd, Gd and Y) and Nd_0.5Sr_0.5MnO₃. Besides discussing the magnetic and electron transport properties, we discuss electric field effects. Rare-earth cobaltates of the type Pr_0.7Ca_0.3CoO₃ and Gd_0.5Ba_0.5CoO₃ also exhibit interesting magnetic and electron transport properties which can be understood in terms of phase separation.