Paramagnetic resonance and susceptibility of ilmenite, FeTiO3 crystal

Abstract

Large high-purity single crystals of FeTiO3 with ilmenite structure have been grown from a stoichiometric melt of Fe2O3 and TiO2 under an inert atmosphere using the modified Czochralski technique. Susceptibility and x-band paramagnetic resonance studies have been performed. Susceptibility measurements indicate a Néel temperature ∼59 K. The paramagnetic resonance spectrum for magnetic field perpendicular to the crystal c axis consists of a portion of a single, very intense approximately Lorentzian absorption line with its peak at about 600 G and half width at half maximum almost 1200 G. The absorption extends to zero magnetic field. For magnetic field approximately parallel to the c axis, the paramagnetic absorption is much smaller and may be considered a superposition of two approximately Lorentzian line shapes. The magnetic resonance measurements indicate a weak temperature dependence and large angular anisotropy.

Magnetic metastability in natural hemo-ilmenite solid solution (y≈0.83)

“…ESR silent. Since Fe (II) is the dominant iron species in our solid solution, isolated Fe (II) species are rather unlikely [30]. Similar signals were described for paramagnetic Fe (III) in layered TlGaSe 2 single crystals [31].…”

Ion irradiation damage in ilmenite at 100 K

“…In nature, ilmenite is by far the most common of the rhombohedral titanates. Ilmenite &,of interest as a potential substrate material for high T, superconducting films [7], as a high-temperature, wide band gap semiconductor [8], and as a component of heavy concrete for radiation shielding in fission reactors [e.g., 91. Ilmenite has been studied as a source for oxygen on proposed lunar bases [lo], as a resource for He3+ for space fusion energy applications [ 1 11, and as a radiation-resistant semiconductor for satellites and related space applications [ 121.…”

Interface magnetism inFe2O3/FeTiO3heterostructures

“…At RT the magnetic moments of subsequent iron layers couple antiferromagnetically (AFM) in-plane with a small spin-canting, attributed to spin-orbit coupling [16,17,18]. In ilmenite, FeTiO 3 , Fe-and Ti-layers alternate, reducing the symmetry to R3 and the corresponding sequence is 3O 2− /2Fe 2+ /3O 2− /2Ti 4+ with AFM coupling between the Fe layers and T N =56-59 K [19].…”

“…At RT the magnetic moments of subsequent iron layers couple antiferromagnetically (AFM) in-plane with a small spin-canting, attributed to spin-orbit coupling [16,17,18]. In ilmenite, FeTiO 3 , Fe-and Ti-layers alternate, reducing the symmetry to R3 and the corresponding sequence is 3O 2− /2Fe 2+ /3O 2− /2Ti 4+ with AFM coupling between the Fe layers and T N =56-59 K [19].At the interfaces (IFs) in hematite-ilmenite exsolutions, charge neutrality is disrupted. One way to balance the excess charge at the interface is by a disproportionation in the Fe layer, now becom- * Electronic address: pentcheva@lrz.uni-muenchen.de ing mixed Fe 2+ and Fe 3+ .…”