Transition from a hysteresis-like to an exchange-bias-like response of an uncompensated antiferromagnet

Highly Co-doped ZnO shows uncompensated antiferromagnetic order and a vertical exchange bias shift even in the absence of a ferromagnet. Therefore, it is an ideal model system to study the behavior of uncompensated antiferromagnetic moments, which play a crucial role in the description of conventional exchange bias. Temperature- and cooling-field-dependent magnetometry measurements provide further information on the compensated and uncompensated antiferromagnetic configurations in Co-doped ZnO, revealing that observed effects of both vertical exchange shift and open hysteresis stem from similar magnetic configurations. This transition is evidenced by the increase of the vertical exchange shift on the expense of the hysteresis opening by lowering the temperature.