Exchange bias induced by CoMn ₂ O ₄ interface grown through sequential annealing in Mn ₂ O ₃ @Co ₃ O ₄ core–shell nanocomposite

Abstract Exchange interactions at the interfaces are the root to produce conventional exchange bias in ferromagnet/antiferromagnet (FM/AFM) heterostructures, which are extensively utilized in spintronics. This work proposes an unconventional approach for the growth of the CoMn 2 O 4 interface in Mn 2 O 3 @Co 3 O 4 core–shell, which led to an unprecedented exchange bias. Specimens were prepared with a modified two‐step co‐precipitation method followed by the controlled heating episodes, to initiate the Co 2+/3+ /Mn 2+/3+/4+ cation exchange, which facilitates CoMn 2 O 4 interface in the sample (SA‐1). For comparison, Mn 2 O 3 @Co 3 O 4 composite was synthesized with inhibited cation exchange (SA‐2 specimen). X‐ray diffraction and high‐resolution transmission electron microscope results confirmed the presence of each phase with core–shell type morphology. SA‐1 sample experiences AFM–FiM (ferrimagnetic) exchange coupling, revealed by the strongly bifurcated zero field‐cooled and field‐cooled magnetization curves below the Néel temperature ( T N ‐86 K), resulting in large exchange bias field ( H EB ) strength of 2712 Oe. Training effect data fitted with thermal relaxation and frozen‐rotatable spin relaxation model suggests the dominant character of uncompensated rotating spins in AFM–FiM–AFM interfaces as opposed to the relaxing frozen spins found in conventional AFM–FM interfaces.