Effect of shell ratio on Mn/Co2+/3+ cation distribution and exchange anisotropy behavior in spinel interphase supported Mn2O3–Co3O4 nanostructures

Abstract

This study demonstrates a strategy for designing and manufacturing a novel core-shell Mn₂O₃-Co₃O₄ nanostructure for significantly enhanced exchange anisotropy or exchange bias (EB) properties via a two-step seeded growth mechanism. The modified chemical route establishes cation exchange between Mn^2+/3+ and Co^2+/3+ ions, forming a novel interphase, i.e., CoMn₂O₄, which served as an efficient channel for altering the physical properties of the prepared nanostructures. Here, we provide experimental evidence of interphase driven magnetic and EB attributes in Mn₂O₃-Co₃O₄. Structural and morphological results asserted three distinct phases within the core-shell-like morphology. Furthermore, the CoMn₂O₄ interface enabled modified cationic distribution was investigated through XPS which indicated, the preferable cationic arrangements as Co³⁺Mn²⁺Mn³⁺O^-8. Magnetic results unveil strong ferrimagnetic (FIM) contribution within antiferromagnetic (AFM) regions resulting in large thermomagnetic irreversibility below the blocking temperature. Effective AFM/FIM coupling generates exchange anisotropy, results in enormous EB that exhibits a proportional dependence on the CoMn₂O₄ phase. Training effect in terms of field cycle variation was also investigated, and fitted with a thermal relaxation model. The remarkable EB and coercivity (H_C) values accompanied by nearly no training effect advocate the resilience and superiority of these compounds in the technological realms of magnetic memory devices and spintronics applications.