Negative magnetization, magnetic anisotropy and magnetic ordering studies on Al3+-substituted copper ferrite

Abstract Detailed magnetic properties of Al 3+ -modified CuFe 2 O 4 spinel ferrite system: CuAl x Fe 2− x O 4 ; x  = 0.0, 0.2, 0.4 and 0.6, have been studied by means of X-ray powder diffraction, field cooled (FC) and zero field cooled magnetization (ZFC) ( H  = 10 mTesla, T  = 4–325 K), magnetic hysteresis ( H ma x  = 2 Tesla, T  = 10 and 300 K) and low field (40 A/m) ac susceptibility ( T  = 300–750 K) measurements. The system exhibits canted spin structure. It has been shown that the observed features of the FC–ZFC magnetization and ac susceptibility curves arise due to the low magneto crystalline anisotropy, not due to the cluster spin-glass-like magnetic ordering. The interesting features like low temperature cusp in the ZFC magnetization for all the compositions and negative magnetization for x  = 0.6 composition have been observed. An attempt has been made to explain the negative magnetization within the framework of available models.