Comparison of the zero-field-cooled magnetization behavior of some ferromagnetic and ferrimagnetic systems

The zero-field-cooled (ZFC) magnetization behavior of two ferromagnetic oxides, SrRuO3 and La2/3Ca1/3MnO3, and two ferrimagnetic oxides, MnCo2O4 and NiFe2O4, has been compared. It has been observed that a peak or maximum in MZFC(T) is obtained (at Tp≤Tc) in a given temperature range only when measured with magnetic fields less than a critical value, Hcr, which is temperature dependent. Hcr corresponds to the field below which the contribution to initial magnetization is mainly from domain wall displacements. MZFC increases with increasing temperature as long as Hcr is greater than the applied field and the applied magnetic field overcomes this critical field above Tp. The results indicate that there is a direct correlation between the shapes of MZFC(T) curves and the domain structure of a material. A drastic decrease of MZFC below Tp is observed for high coercivity (hard) materials when measured with small DC magnetic fields, compared to a broad maximum obtained for the soft materials, because of domain wall pinning effects