Magnetic properties and exchange bias effect of Y_2−xSr_xCoMnO₆ (0 ≤ x ≤ 0.5) double perovskites

The structural and magnetic properties of Y_2−xSr_xCoMnO₆ (0 ≤ x ≤ 0.5) compounds are investigated in this report. X-ray photoelectron spectroscopy reveals that Co and Mn ions are presented in the form of Co²⁺/Co³⁺ and Mn³⁺/Mn⁴⁺, respectively. The broadening of Raman spectra suggests the existence of antisite disorders in these double perovskite oxides. The ferromagnetic transition temperature slightly increases with Sr doping, while the saturated magnetic moment shows a substantial decrease, further confirming the presence of Co/Mn antisite disorders. The signature of exchange bias effect in Y_2−xSr_xCoMnO₆ (0 ≤ x ≤ 0.5) double perovskites has been observed, which is demonstrated by the displacement of field-cooled magnetic hysteresis loops. Moreover, the exchange bias field is strongly correlated with the degree of antisite disorders and reaches a maximum of 3.4 kOe for x = 0.25. The origin of exchange bias effect can be explained as the interfacial exchange coupling between ferromagnetic regions and antiferromagnetic antiphase boundaries created by antisite disorders in these specimens.