Enhancing low-field magnetoresistance in magnetite nanoparticles via zinc substitution

Abstract

We report a strategy to enhance the room temperature low-field magnetoresistance (LFMR) behavior of Fe₃O₄ nanoparticle (NP) assemblies by controlled Zn-substitution. The Zn-substituted 7 nm Zn_xFe_3−xO₄, (x = 0 to 0.4) NPs are prepared by thermal decomposition of metal acetylacetonates (M(acac)_n, M = Fe²⁺, Fe³⁺, and Zn²⁺). The substitution increases NP magnetic susceptibility (χ) and makes the magnetic moment more sensitive to low magnetic fields. As a result, the Zn_0.3Fe_2.7O₄ NP assembly with NPs separated by tridecanoate exhibits a large magnetoresistance (MR) ratio of −14.8% at 300 K under a 4.5 kOe magnetic field. The demonstrated approach to control NP substitution to enhance low-field magnetoresistance of the NP assemblies provides an attractive new strategy to fabricate Fe₃O₄-based magnetic NP assemblies with desirable transport properties for sensitive spintronic applications.