Unstrained epitaxial Zn-substituted Fe₃O₄ films for ferromagnetic field-effect transistors

A field-effect transistor has been fabricated utilizing an epitaxial film of unstrained zinc-substituted magnetite (Fe₃O₄) as the active channel. A thin film of Fe_2.5Zn_0.5O₄ was grown on a lattice-matched MgO(001) substrate by pulsed-laser deposition and covered by a parylene gate insulator to dope charge carriers by a field effect. The device showed a field-effect mobility of 1.2 × 10^-2 cm ² V^-1 s^-1 at 300 K, which is higher by a factor of 15 than those of the devices with strained Fe_2.5Zn _0.5O₄ channels on perovskite-type substrates. The enhanced response to the gate electric field is useful in exploring gate-tunable magnetism in magnetite.