Effect of Vanadium Doping on the Structural and Magnetic Properties of Lao.5Sro.5Co03-a

Abstract

In this work, the effect of Vanadium doping on the oxidation states of cobalt ions in Lao.5Sro.5Co03-1l system have been studied by using structural and magnetic measurements_ Polycrystalline samples LaO.5 Sro.5C003-1l and La0.5Sro.5COO.9VO.,03-1l were prepared by cost effective solid-state reaction technique_ Structural analysis of both the prepared samples were studied by using X-ray diffraction technique. Doping effect of vanadium in LaO.5SrO.5C003-1l is carefully observed and analysed in detail. In-phase Cl) and out-phase exl!) component of ac magnetic susceptibility of both polycrystalline samples LaO.5SrO.5Co03-a and Lao.5SrO.5COO.9 VO.,03-a have been measured as a function of temperature at various frequencies and at various applied magnetic fields. Spin glass behaviour and their corresponding freezing temperatures have been observed for both these samples. Mydosh parameter and Vogel-Fulcher law was used to confinn the spin glass behaviour. It was observed that, the disorder in the LaO.5SrO.5Co03-a system decreases due to vanadium doping_ Detailed magnetic measurements shows the decrease of transition temperature with vanadium doping indicating the weakening of double exchange ferromagnetic interaction between Co3+ and Co4 + ions and strengthening of super-exchange anti-ferromagnetic interactions between C03+-0- Co3+ and Co4+-0- Co4 + coupling. Furthennore, it was also found that susceptibility was dramatically suppressed at higher magnetic fields.