On the observation of negative magnetization under zero-field-cooled process

We have addressed problems associated with the measurement of zero-field-cooled (ZFC) magnetization and its interpretation in the light of negative magnetization reported in certain ferrimagnetic materials such as CoCr2O4. We demonstrate that a small negative trapped field in the sample space as well as large coercive fields are responsible for the observed negative magnetization. The problem is commonly encountered while working with magnetometers and a superconducting magnet where the sign of the trapped field can be positive or negative depending on the way the field is reduced to zero.