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)[Formula see text] (GdCrO3) x (where [Formula see text]), which resides between orthorhombic ferromagnetic (FM) metal SrRuO3 ([Formula see text] K) and orthorhombic antiferromagnetic (AFM) insulator GdCrO3 ([Formula see text] K). Crystal structure analysis reveals that complete solid solution exists only up to [Formula see text], above which chemical phase separation of two/three phases occurs, and persists up to [Formula see text]. X-ray photoelectron spectroscopy measurement also corroborates the existence of [Formula see text] for the intermediate composition [Formula see text], which reinforces the astonishing scheelite-type GdCrO4 formation (at ambient pressure) for [Formula see text] compositions. Electrical resistivity measurements affirm the temperature driven metal to insulator (M-I) transition for [Formula see text] and [Formula see text] 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 [Formula see text] 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 (T C), and thereby introduces Griffiths phase in phase separated samples. Furthermore, we believe that a sharp rise in magnetization at low temperature for [Formula see text] samples is due to the formation of AFM GdCrO4 phase. Prominent thermal hysteresis in temperature dependent magnetization curves for [Formula see text], and appearance of spin-reorientation transition for [Formula see text] are the distinct indications for transformation into canted AFM GdCrO3 oxide at higher x. The effective magnetic moment ([Formula see text]) continuously increases with the incorporation of higher moment elements (Gd and Cr); while coercive field (H C) exhibits an abrupt variation as a function of x at the onset of phase separation.