LAUSR

We investigated the electrical properties of Fe3O4 films grown on MgO (001) substrates by pulsed-laser deposition for use as high-temperature resistors. By systematically examining the thickness-dependent resistivity and magnetoresistance, we found that a film thickness of approximately 200 nm was critical to obtaining a small, bulk-like temperature coefficient of resistance at high temperature. We improved the thermal stability of Fe3O4 films by surface passivation with an insulating Al2O3 layer. By combining these findings, we achieved a resistance change as small as 13% over a temperature range of −40 °C to 250 °C, satisfying a basic requirement of high-temperature resistors.