Coexistence of magnetization reversal and exchange bias in Mn-substituted CuCrO2

We systematically studied the magnetization reversal (MR) and exchange bias (EB) properties of Mn-doped CuCrO2 compounds. Single-phase ceramic samples of CuCr1−xMnxO2 (x = 0-0.2) were synthesized with the sol-gel method. Synchrotron radiation X-ray absorption spectroscopy of the Mn 2p, Cr 2p core levels showed that the Cr ion is trivalent and the Mn ion is in a mixed valence state of Mn3+/4+. All the Mn-doped samples, due to the double-exchange interaction between Cr3+-O-Mn3+ and Mn3+-O-Mn4+, showed a ferromagnetic transition in field-cooling magnetization. Interestingly, zero-field-cooling magnetization reversed from positive to negative as temperature decreased below the compensation temperature. The x = 0.05 sample also showed exchange bias. The coexistence of MR and EB in the system can be explained by the competition between ferromagnetic and antiferromagnetic order.