Anomalous low temperature magnetic behaviour of Ca2Fe2(1-x)Cr2xO5 (x = 0, 0.1 and 0.2)

Abstract

In the present study, systematic investigations on structural, magnetic, and thermal properties of a series of polycrystalline samples Ca2Fe2(1-x)Cr2xO5 (x = 0, 0.1, and 0.2) are reported. These compounds have been successfully synthesised by solid-state reaction method and are found to crystallise in brownmillerite orthorhombic structures with space group Pnma. In the case of the parent compound Ca2Fe2O5, a negative magnetisation (sign reversal of magnetisation) is observed in temperature-dependent magnetic study, which is anticipated to arise from multiple sublattice interactions. On the other hand, isothermal magnetisation studies exhibit the presence of weak ferromagnetic coupling in Ca2Fe2O5. From Magnetocaloric calculations, it is evident that antiferromagnetic interactions are predominant at the low-temperature regime (below 150 K). The partial substitution of Cr in place of Fe leads to a remarkable change in the magnetic behaviour of the compound along with suppression of negative magnetisations and ferromagnetic interactions. Additionally, the Differential Scanning Calorimetry study indicates a gradual shift in magnetic transition temperatures with an increase in Cr substitution.