High frequency magneto-impedance of double perovskite $La_{1.2}Sr_{1.8}Mn_{2}O_{7}$: secondary transitions at high temperatures

Abstract

Radio frequency magneto-impedance measurements clearly reveal a pronounced anomaly at 260K besides the main MI transition at 125K in the double perovskite material $La_{1.2}Sr_{1.8}Mn_{2}O_{7}$. This feature is not seen clearly in static resistivity and magnetization measurements. We suggest that this anomaly represents short range magnetic correlations enhanced at radio frequencies, with the easy axis along the c-axis .