Probing temperature-dependent magnetism in cobalt and zinc ferrites: A study through bulk and atomic-level magnetic measurements for spintronics

Abstract

Spinel ferrites (MFe2O4) are integral to various industries, particularly spintronics, which utilizes the intrinsic spin of electrons as well as the electronic charge to develop devices that dictate spin-based transport, advancing new memory, logic applications, and improving magnetic storage technologies. These materials are valued for their exceptional optical, magnetic and electrical properties, and their easily tunable shape and size. This flexibility of spinel ferrites and their connection to the material’s magnetic behavior can be investigated by studying a range of spinel ferrite structures. In this study, the magnetic behaviors of cobalt ferrite (CFO) and zinc ferrite (ZFO) nanoparticles were examined using a vibrating sample magnetometer (VSM, bulk magnetometry) and X-ray Magnetic Circular Dichroism (XMCD, atomic magnetometry). The Rietveld refinement of XRD data supported single phase spinel structure, while X-ray Absorption Spectroscopy (XAS), particularly through the Co L-edge XANES analysis, detected both Co2+ and Co3+ ions in CFO, suggesting significant ferromagnetic behavior due to octahedral site occupation. In contrast, ZFO exhibited antiferromagnetic character, with Zn2+ ions in tetrahedral sites, and canted antiferromagnetism manifesting as a hysteresis loop below 300 K, potentially related to lattice distortions or strain. At the atomic scale, XMCD analysis, along with sum rules, estimated the average magnetic moments for cobalt and zinc ferrites to be 3.045 ± 0.1 (1.448 ± 0.1) and 0.657 ± 0.1 (2.12 ± 0.1) μB at temperatures of 300 K (90 K), respectively. However, VSM-based bulk measurements indicated magnetic moments of 2.566 (2.288) and 0.281 × 10−3 (0.6503 × 10−3) μB for CFO and ZFO, respectively, at the same temperatures. The observed variation between bulk and atomic-scale magnetic moments points to complex interstitial interactions within the spinel ferrite’s sublattices. This discrepancy between the atomic-scale and bulk magnetic moments suggests intricate interstitial interactions within the spinel ferrite’s sublattices. These insights into the structural and magnetic intricacies of spinel ferrite nanoparticles enhance our understanding, facilitating the design of cutting-edge spintronic devices.