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Magnetic and transport properties of the room-temperature ferrimagnetic semiconductor Fe1.5Ti0.5O3± delta: Influence of oxygen stoichiometry

Fe1.5Ti0.5O3± delta epitaxial thin films have been grown on alpha-Al2O3 (0001) substrates by pulsed laser deposition technique. The samples are both ferrimagnetic and semiconducting beyond room temperature. Oxygen pressure (PO2) during the deposition appears to be a critical parameter in promoting high temperature long range magnetic order and semiconducting properties. For all oxygen pressures, Fe1.5Ti0.5O3± delta thin films are single phase with twin epitaxy. High dc conductivity and low magnetization are obtained at low PO2, whereas high saturation magnetization and low conductivity stand for high PO2. Oxygen vacancies and/or change of iron valence state are pointed out to be responsible of these properties. Superexchange mechanism via oxygen bonds seems rather to dominate the magnetic properties especially for high PO2, whereas for low PO2 a double exchange mechanism might occur. Fe1.5Ti0.5O3± delta appears thus to be an interesting material for high temperature spintronics applications.

electrical conductivity; ferrimagnetic materials; iron compounds; long-range order; magnetic epitaxial layers; magnetic semiconductors; magnetisation; pulsed laser deposition; stoichiometry; superexchange interactions; titanium compounds; vacancies (crystal)

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