Exchange bias induced by CoMn2O4 interface grown through sequential annealing in Mn2O3@Co3O4 core-shell nanocomposite

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 CoMn2O4 interface in Mn2O3@Co3O4 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 Co2+/3+/Mn2+/3+/4+ cation exchange, which facilitates CoMn2O4 interface in the sample (SA-1). For comparison, Mn2O3@Co3O4 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 N & eacute;el 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.