Effect of Gd and Cr substitution on the structural, electronic and magnetic phases of SrRuO3: a case study of doping and chemical phase separation

Abstract

We explore the crystal structure, electrical resistivity and magnetic behavior of the compositional series (SrRuO3) (GdCrO3)x (where ), which resides between orthorhombic ferromagnetic (FM) metal SrRuO3 ( K) and orthorhombic antiferromagnetic (AFM) insulator GdCrO3 ( K). Crystal structure analysis reveals that complete solid solution exists only up to , above which chemical phase separation of two/three phases occurs, and persists up to . X-ray photoelectron spectroscopy measurement also corroborates the existence of for the intermediate composition , which reinforces the astonishing scheelite-type GdCrO4 formation (at ambient pressure) for compositions. Electrical resistivity measurements affirm the temperature driven metal to insulator (M–I) transition for and samples. Low temperature insulating state in these samples is interpreted by electron–electron interaction of weak disordered systems. Precise analysis of temperature dependent resistivity for samples (which have insulating ground state) dictate that the transport phenomenon is mainly associated with Arrhenius-type charge conduction, Mott’s variable range hopping, short-range and long-range Coulomb interaction mediated hopping processes, due to the high degree of randomness. Interruption of magnetic Ru–O–Ru interaction by Ru–O–Cr and Cr–O–Cr interactions lowers the FM transition temperature (TC), and thereby introduces Griffiths phase in phase separated samples. Furthermore, we believe that a sharp rise in magnetization at low temperature for samples is due to the formation of AFM GdCrO4 phase. Prominent thermal hysteresis in temperature dependent magnetization curves for , and appearance of spin-reorientation transition for are the distinct indications for transformation into canted AFM GdCrO3 oxide at higher x. The effective magnetic moment () continuously increases with the incorporation of higher moment elements (Gd and Cr); while coercive field (HC) exhibits an abrupt variation as a function of x at the onset of phase separation.