The morphology, structure, and magnetic properties of the magnetic semiconductor ceramic Ilmenite-Hematite (IH), (1Àx)Fe-TiO 3 -xFe 2 O 3 , were studied as a function of the composition x. The magnetic ordering temperatures that we observed were consistently higher than those reported previously and were, for most of the composition range, above room temperature. We rule out the formation of Fe clusters as the origin of the magnetic properties. These magnetic properties of IH ceramics, in combination with their semiconducting characteristics, render them promising for spin-electronic applications. 1601J ournal

We demonstrated the capability of MeV proton irradiation to promote chemical ordering processes in a solid at low temperature. We used the ilmenite–hematite solid solution system which allows estimation of the degree of ordering through measurement of its magnetization. Normally, ordering through diffusion would require high temperature annealing. At high temperatures, however, the equilibrium state would be less ordered and thus the achievable ordering incomplete. High energetic protons continuously transfer energy to the sample through electronic interaction which locally deposits large quantities of energy without a general increase of the sample temperature. This promotes diffusion processes which allow the system to relax towards the ordered equilibrium state.

The solid solution system ilmenite-hematite [(FeTiO3)1−x–(Fe2O3)x] is a potential candidate for applications in spintronics due to its intrinsic ferrimagnetic and semiconducting properties. Epitaxial ilmenite-hematite films with x=0.33, which have the highest room temperature magnetic moment, were grown on α-Al2O3 (0001) substrates using pulsed laser deposition technique with varying oxygen partial pressure in the ambient gas. Structural, magnetic, electrical, and optical properties are found to be largely dependent on the oxygen content of the films which is controlled by substrate temperature and ambient gas composition. The highest crystalline and magnetic ordering and the lowest resistivity values could be obtained for growth at high temperatures and under low oxygen pressure. A narrowing of the band gap (to around 2.4eV) was observed for films grown under high oxygen pressure in comparison with films grown in vacuum or argon (around 3.3eV).

Ilmenite-hematite [(FeTiO3)1−x–(Fe2O3)x] is a solid solution system with intrinsic ferrimagnetic and semiconducting properties. Bulk ceramic samples and epitaxial thin films have been prepared with magnetization values of up to 1500G (bulk) and 700G (thin films) at room temperature. Superparamagnetic behavior was discriminated from ferrimagnetic properties using field cooled and zero field cooled measurements. The blocking temperature exceeds room temperature for samples with composition x>0.25. Using magnetic force microscopy, the domain structure in the thin ilmenite-hematite films was detected.

The ilmenite-hematite (1 -x) FeTiO 3 Á xFe 2 O 3 solid solution system is considered to be a novel material for spin-electronics, microelectronics, hightemperature electronics, and radhard electronics. This paper focuses on thin films of composition x = 0.33 grown on (100) MgO single-crystal substrates using pulsed-laser deposition (PLD) under different argon-oxygen mixtures. The surface of the MgO was found to possess MgO 2 crystals, yielding an orientation relationship, [001] MgO k [011] MgO 2 and (100)MgO k (110) MgO 2 . The structural characterizations show that the films are crystalline and homogeneous without any secondary phase. The films show a weak and inclined (1120) growth epitaxy. A bandgap of 3.4-3.7 eV was obtained for these films from optical measurements carried out in the UV-visible region. Electrical measurements confirmed the semiconducting behavior. However, the resistivity was found to increase substantially on the slightest addition of oxygen into the chamber.