Electrical- and magneto-resistance control for magnetite nanoparticle sinter by regulation of heat treatment temperature

► We investigated electrical- and magneto-resistance controls in magnetite (Fe3O4) nanoparticle sinter (MNPS) by the regulation of heat treatment (HT) temperature. ► By changing the HT temperature, the coupling state between adjacent magnetite nanoparticles and the crystallinity of MNPS were altered. ► Below ∼600 °C, ER and MR were dominated by grain-boundary conduction, while above ∼600 °C they were determined by inter-grain conduction. ► The application of a magnetic field to the grain-boundary region, which had relatively random localized spins, caused a large enhancement in MR.