Magnetic Properties of the FeTiO3-Fe2O3 Solid Solution Series

Ishikawa, Yoshikazu; Akimoto, Syun‐iti

doi:10.1143/jpsj.12.1083

Cited by 176 publications

(143 citation statements)

References 21 publications

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“…Still, some degree of Ti disorder is likely in quickly cooled samples, reducing the expected magnetization as observed by Chambers et al [3] (0.5±0.15µ B /Ti for x Ti = 0.15). For higher Ti concentrations and longer annealing steps the formation of the thermodynamically more stable layered ferrimagnetic phase is expected, consistent with the strong correlation between cation order and ferrimagnetism found in annealed samples [8,12] and the saturation magnetization of 3µ B /mol measured in epitaxial films with x Ti ≤ 0.63 [13]. While below the ordering temperature of ilmenite only ilmenite lamella with an odd number of Ti-layers are expected to carry a non-zero magnetization, above 56 K the net magnetic moment will be solely due to the uncompensated magnetic moments in the contact layers, independent of the number of Ti-layers within the paramagnetic ilmenite lamella.…”

Section: Or T 58supporting

confidence: 77%

“…On the other hand, using the ilmenite lattice parameters at x = 66% instead of hematite (volume increase of 8.7%) leads to an energy gain of 0.22 eV/p.f.u. for T 7,8,11,12 (red filled up-triangles in Fig. 3).…”

Section: Or T 58mentioning

confidence: 99%

“…Most of the efforts concentrate on homogeneous doping of semiconductors with magnetic impurities [1,2,3,4], but the interfaces in complex oxides prove to be another source of novel behavior [5,6,7]. The unique magnetic properties of the hematiteilmenite system [8,9,10] (a canted antiferromagnet and a RT paramagnet, respectively) currently receive revived interest as a possible cause of magnetic anomalies in the Earth's deep crust and on other planets [11] as well as for future device applications [3,12,13].…”

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confidence: 99%

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Interface magnetism inFe2O3/FeTiO3heterostructures

Pentcheva¹,

Nabi²

2008

Phys. Rev. B

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To resolve the microscopic origin of magnetism in the Fe2O3/FeTiO3-system, we have performed density functional theory calculations taking into account on-site Coulomb repulsion. By varying systematically the concentration, distribution and charge state of Ti in a hematite host, we compile a phase diagram of the stability with respect to the end members and find a clear preference to form layered arrangements as opposed to solid solutions. The charge mismatch at the interface is accommodated through Ti 4+ and a disproportionation in the Fe contact layer into Fe 2+ , Fe 3+ , leading to uncompensated moments in the contact layer and giving first theoretical evidence for the lamellar magnetism hypothesis. This interface magnetism is associated with impurity levels in the band gap showing halfmetallic behavior and making Fe2O3/FeTiO3 heterostructures prospective materials for spintronics applications.A challenge of today's materials science is to design ferromagnetic semiconductors operating at room-temperature (RT) for spintronics devices. Most of the efforts concentrate on homogeneous doping of semiconductors with magnetic impurities [1,2,3,4], but the interfaces in complex oxides prove to be another source of novel behavior [5,6,7]. The unique magnetic properties of the hematiteilmenite system [8, 9, 10] (a canted antiferromagnet and a RT paramagnet, respectively) currently receive revived interest as a possible cause of magnetic anomalies in the Earth's deep crust and on other planets [11] as well as for future device applications [3,12,13].Both hematite (a = 5.035Å, c = 13.751Å [14]) and ilmenite (a = 5.177Å, c = 14.265Å [15]) crystallize in a corundum(-derived) structure shown in Fig. 1 where the oxygen ions form a distorted hexagonal close packed lattice and the cations occupy 2/3 of the octahedral sites. In α-Fe 2 O 3 (space group R3c) there is a natural modulation of electronic density along the [0001]-direction where negatively charged 3O 2− layers alternate with positively charged 2Fe 3+ layers. 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+ . This lamellar magnetism hypothesis (LMH) was proposed by Robinson et al. [20] based on bond valence models and kinetic Monte Carlo simulations (kMC) with empirical chemical and magnetic interaction parameters. The increased technological interest in this system calls for an atomistic material specific understanding that can only be obtained from first principles calculatio...

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Section: Or T 58supporting

confidence: 77%

Section: Or T 58mentioning

confidence: 99%

mentioning

confidence: 99%

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Interface magnetism inFe2O3/FeTiO3heterostructures

Pentcheva¹,

Nabi²

2008

Phys. Rev. B

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“…An ilmenite-hematite solid solution ͑Fe 2-x Ti x O 3 ͒ is one of the candidates for nontraditional magnetic semiconductors because intermediate compositions between ilmenite ͑FeTiO 3 ͒ and hematite ͑␣-Fe 2 O 3 ͒ are known to be both semiconducting and ferrimagnetic. [4][5][6] A recent theoretical calculation has predicted that Fe 2-x Ti x O 3 is a strong candidate for a magnetic semiconductor with strong spin-dependent transport properties and a high Curie temperature above 400°C. [7][8][9] Moreover, a solid solution system can produce either an n-type or a p-type semiconductor by changing the Fe-to-Ti concentration ratio.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, Hojo et al have succeeded in preparing room temperature ferrimagnetic Fe 1. 4 Ti 0.6 O 3 films with R3 symmetry by the pulsed laser deposition technique. 10,11 The spin polarization of n-type carriers in Fe 1.…”

Section: Introductionmentioning

confidence: 99%

Preparation and characterization of epitaxial Fe2−xTixO3 films with various Ti concentrations (0.5<x<1.0)

Takada

Nakanishi

Fujii

et al. 2008

Journal of Applied Physics

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An ilmenite-hematite solid solution ͑Fe 2-x Ti x O 3 ͒ is one of the candidates for practical magnetic semiconductors with a high Curie temperature. We have prepared well-crystallized epitaxial Fe 2-x Ti x O 3 films with a wide range of Ti concentrations-x = 0.50, 0.60, 0.65, 0.76, 0.87, and 0.94-on ␣-Al 2 O 3 ͑001͒ substrates. The films are prepared by a reactive helicon plasma sputtering technique to evaporate Fe and TiO targets simultaneously under optimized oxygen pressure conditions. The structural characterizations of the films reveal that all films have a single phase of the ordered structure with R3 symmetry, where Ti-rich and Fe-rich layers are stacked alternately along the c axis. All films have large ferrimagnetic moments at low temperature, and room temperature magnetization is clearly observed at x Ͻ 0.7. The inverse temperature dependence of the resistivities of the films indicates their semiconducting behavior. The film resistivities decrease with decreasing Ti concentration.

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Importance of titanohematite in detrital remanent magnetizations of strata spanning the Cretaceous‐Paleogene boundary, Hell Creek region, Montana

Sprain

Feinberg

Renne

et al. 2016

Geochem Geophys Geosyst

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Intermediate composition titanohematite, Fe 2-y Ti y O 3 with 0.5 y 0.7, is seldom the focus of paleomagnetic study and is commonly believed to be rare in nature. While largely overlooked in magnetostratigraphic studies, intermediate titanohematite has been identified as the dominant ferrimagnetic mineral in an array of Late Mesozoic and early Cenozoic Laramide clastic deposits throughout the central United States. Intermediate titanohematite is ferrimagnetic and has similar magnetic properties to titanomagnetite, except its unique self-reversing property. Due to these similarities, and with detrital remanent magnetizations masking its self-reversing nature, intermediate titanohematite is often misidentified in sedimentary deposits. Past studies relied upon nonmagnetic techniques including X-ray diffraction and electron microprobe analysis. While these techniques can identify the presence of intermediate titanohematite, they fail to test whether the mineral is the primary recorder. To facilitate the identification of intermediate titanohematite in sedimentary deposits, we characterize this mineral using low-temperature magnetometry and high-temperature susceptibility experiments, and present a new identification technique based on titanohematite's self-reversing property, for sediments that span the Cretaceous-Paleogene boundary (Hell Creek region, Montana). Results from the self-reversal test indicate that the majority of remanence is held by minerals that become magnetized parallel to an applied field, but that intermediate, selfreversing titanohematite (y 5 0.53-0.63) is an important ancillary carrier of remanence. While earlier literature suggests that intermediate titanohematite is rare in nature, reanalysis using specialized rock magnetic techniques may reveal that it is more abundant in the rock record, particularly within depositional basins adjacent to calc-alkaline volcanics, than previously thought.

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Magnetic Properties of the FeTiO₃-Fe₂O₃ Solid Solution Series

Cited by 176 publications

References 21 publications

Interface magnetism inFe2O3/FeTiO3heterostructures

Interface magnetism inFe2O3/FeTiO3heterostructures

Preparation and characterization of epitaxial Fe2−xTixO3 films with various Ti concentrations (0.5<x<1.0)

Importance of titanohematite in detrital remanent magnetizations of strata spanning the Cretaceous‐Paleogene boundary, Hell Creek region, Montana

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Magnetic Properties of the FeTiO3-Fe2O3 Solid Solution Series

Cited by 176 publications

References 21 publications

Interface magnetism inFe2O3/FeTiO3heterostructures

Interface magnetism inFe2O3/FeTiO3heterostructures

Preparation and characterization of epitaxial Fe2−xTixO3 films with various Ti concentrations (0.5&lt;x&lt;1.0)

Importance of titanohematite in detrital remanent magnetizations of strata spanning the Cretaceous‐Paleogene boundary, Hell Creek region, Montana

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Magnetic Properties of the FeTiO₃-Fe₂O₃ Solid Solution Series

Preparation and characterization of epitaxial Fe2−xTixO3 films with various Ti concentrations (0.5<x<1.0)