Comparison of the irreversible thermomagnetic behaviour of some ferro- and ferrimagnetic systems

The magnetic behaviour of two ferromagnetic oxides and two ferrimagnetic oxides (ferrites) are compared to study the effect of magnetocrystalline anisotropy on thermal-history-dependence of magnetization of these ordered magnetic systems, All four compounds show thermomagnetic irreversibility (M-FC > M-ZFC) below a certain temperature, T-irr. The highly anisotropic ferromagnetic oxide, SrRuO3 and the hard ferrite, SrFe12O19 show sharp peaks below T-c in their M-ZFC(T) curves, whereas for the soft ferrite Ni0.8Zn0.2Fe2O4 and the lo tv anisotropic ferromagnetic oxide La0.7Ca0.3MnO3 only a broad maximum is observed in M-ZFC, when measured in small magnetic fields. The shapes of the M-ZFC(T) curves are inversely-related to the magnitude of the coercivities (H-c) of the compounds in relation to the applied field, and the temperature dependence of H-c. M-FC and M-ZFC are related through the coercivity for all four magnetic systems.