Hysteresis in magnetoresistance and formation of spin glass like structure in PVA capped Fe3O4

Abstract

Here, we report the temperature dependent hysteresis in the magneto transport in PVA capped Fe3O4 nanoparticles. The synthesis of the nanoparticles of size 10–15 nm were carried out via co-precipitation method followed by heat treatment at different temperatures. Structural studies confirm the formation of polycrystalline Fd $$\bar 3{m}$$ phase of Fe3O4 when the samples were sintered up to 600 °C. FTIR studies show that PVA and magnetic grains were attached through hydrogen bonding between hydroxyl group of PVA and protonated surface of the oxide. Spin glass type transition was observed in the ZFC–FC plots at 125 K which is also the Verwey transition temperature TV as measured from the transport studies. A hysteresis in the MR plot was found which was explained in the realm of tunnel transport through ferromagnetic grain and antiferromagnetic surface of the ferrite particles. Tunnelling through the dielectric spacer layer of PVA has an overall impact to increase the resistance of the samples. The temperature dependence of the hysteresis gives a major hint to the origin of the spin glass type behaviour of the samples.