A systematic variation in cationic distribution and its influence on the magnetization of mixed-metal (nickel and zinc) cobaltite spinels

Abstract

Cobaltite oxide spinel (CoCo2O4) is one promising material that has been extensively studied for decades due to its versatile applications. Revealing the correlation among chemical compositions, cationic distributions, and physical properties are crucial for exploring its novel application. Here, a series of nickel/zinc co-substituted cobaltite spinels, Zn1−XNiXCo2O4 (ZNCO-X; where X = 0.00, 0.25, K, 1.00), was synthesized by calcining the hydrothermal-derived precursors and their magnetic properties have been investigated. Multiple x-ray based characterization techniques (XRD, XRF, XPS, and XAS) were applied to determine the crystalline structure and appropriated compositions of cation species (Zn2+, Ni2+, Ni3+, Co2+, and Co3+). In conjunction with Neel's theory of antiferromagnetism, the theoretical magnetization of the spinel series was calculated based on the assumption that Zn2+ ion was located in tetrahedral (A site) while nickel cations (Ni2+ and Ni3+) occupying the octahedral (B site). The theoretical magnetization profile exhibited a good correlation. Superparamagnetic effect and cationic site exchange can be used to explain the discrepancies between the measured and calculated magnetizations. This work reported a systematic controlling of materials structure and cationic distribution, which are crucial for fine-tuning the magnetic property of the Zn1−XNiXCo2O4 cobaltite system.