Spin Seebeck effect in <i>ɛ</i>-Fe2O3 thin films with high coercive field

Knı́žek, K.; Pashchenko, M. I.; Levinský, Petr; Kaman, Ondřej; Houdková, J.; Jiřı́ček, P.; Hejtmánek, J.; Soroka, Miroslav; Buršík, J.

doi:10.1063/1.5045304

Cited by 14 publications

(11 citation statements)

References 39 publications

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“…4 shows the hysteresis loops measured in the temperature range of 5-400 K and corrected for the linear diamagnetic contribution of the substrate. The observed values of saturation magnetization were about 130 emu/cm 3 at T = 5 K and 100 emu/cm 3 at T = 400 K which is consistent with what was reported for ε-Fe 2 O 3 nanoparticles 38 and ε-Fe 2 O 3 thin film grown on SrTiO 3 (STO) 12 , YSZ 19,39 and GaN 22 , and predicted from ab-initio calculations 15 .…”

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confidence: 89%

Stabilization of ε−Fe2O3 epitaxial layer on MgO(111)/GaN via an intermediate γ -phase

Ukleev

Волков

Korovin

et al. 2019

Phys. Rev. Materials

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In the present study we have demonstrated epitaxial stabilization of the metastable magneticallyhard ε-Fe2O3 phase on top of a thin MgO(111) buffer layer grown onto the GaN (0001) surface. The primary purpose to introduce a 4 nm-thick buffer layer of MgO in between Fe2O3 and GaN was to stop thermal migration of Ga into the iron oxide layer. Though such migration and successive formation of the orthorhombic GaFeO3 was supposed earlier to be a potential trigger of the nucleation of the isostructural ε-Fe2O3, the present work demonstrates that the growth of single crystalline uniform films of epsilon ferrite by pulsed laser deposition is possible even on the MgO capped GaN. The structural properties of the 60 nm thick Fe2O3 layer on MgO / GaN were probed by electron and x-ray diffraction, both suggesting that the growth of ε-Fe2O3 is preceded by formation of a thin layer of γ-Fe2O3. The presence of the magnetically hard epsilon ferrite was independently confirmed by temperature dependent magnetometry measurements. The depth-resolved x-ray and polarized neutron reflectometry reveal that the 10 nm iron oxide layer at the interface has a lower density and a higher magnetization than the main volume of the ε-Fe2O3 film. The density and magnetic moment depth profiles derived from fitting the reflectometry data are in a good agreement with the presence of the magnetically degraded γ-Fe2O3 transition layer between MgO and ε-Fe2O3. The natural occurrence of the interface between magnetoelectric ε-and spin caloritronic γ-iron oxide phases can enable further opportunities to design novel all-oxide-on-semiconductor devices.The magnetic-on-semiconductor heterostructures attract a lot of interest nowadays due to the vast opportunities they provide for designing novel functional spintronic devices for magnetic memory applications and bioinspired computing 1-7 . Placing a multiferroic layer with controllable magnetization/polarization in contact with a semiconductor adds the functionality of controlling optical, electronic and magnetic properties of the heterostructure by applied voltage 8-11 . One of the rare examples of material with spontaneous room-temperature magnetization and electric polarization is the metastable iron(III) oxide polymorph ε-Fe 2 O 3 12-15 . Quite recently, the crystalline layers of ε-Fe 2 O 3 have been successfully synthesized on a number of oxide substrates 12,16-20 and GaN(0001) 21 . The structural and magnetic properties of the iron oxide films drastically depend on the composition of the neighboring buffer layer, the chosen substrate and the growth temperature. The feasibility to synthesize as much as four different iron oxide phases: ε-Fe 2 O 3 , Fe 3 O 4 , α-Fe 2 O 3 and γ-Fe 2 O 3 on GaN(0001) by fine adjustment of growth parameters has been recently demonstrated 21 . It has been shown that stabilization of the ε-Fe 2 O 3 phase requires elevated growth temperature that leads to formation of a few nanometer-thick Ga-rich magnetically soft transition layer at the interface between the iron oxide film ...

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confidence: 89%

Stabilization of ε−Fe2O3 epitaxial layer on MgO(111)/GaN via an intermediate γ -phase

Ukleev

Волков

Korovin

et al. 2019

Phys. Rev. Materials

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“…Epsilon iron oxide (ε‐Fe 2 O 3 ) nanomagnets are attractive because they have been reported to exhibit a large coercive field and high‐frequency millimeter‐wave absorption at 182 GHz by zero‐field ferromagnetic resonance (the so‐called natural resonance). [ 17–48 ] Metal‐substituted epsilon iron oxide (ε‐ M x Fe 2− x O 3 : M = Al 3+ , Ga 3+ , and In 3+ ) and Ti 4+ −Co 2+ cosubstituted series, ε‐(TiCo) x Fe 2− x O 3 , exhibit zero‐field ferromagnetic resonance over a wide frequency range of 35–182 GHz. Rhodium‐substituted epsilon iron oxide, ε‐Rh x Fe 2− x O 3 , shows even higher resonance frequencies above 182 GHz by increasing the Rh/Fe ratio.…”

Section: Introductionmentioning

confidence: 99%

Resonance Frequency Tuning of a 200 GHz Band Absorber by an External Magnetic Field

Tsukamoto

Oki

Imoto

et al. 2022

Advanced Photonics Research

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The effect of the external magnetic field on the millimeter‐wave absorption of rhodium‐substituted epsilon iron oxide, ε‐Rh0.13Fe1.87O3 (1) and ε‐Rh0.19Fe1.81O3 (2) nanomagnets, is investigated. Terahertz time‐domain spectroscopy (THz‐TDS) shows that 1 and 2 display a zero‐field ferromagnetic resonance (the so‐called natural resonance) at 201 GHz with a linewidth of 20 GHz and at 210 GHz with a linewidth of 30 GHz, respectively. The ferromagnetic resonance is measured under an external magnetic field (H ex). Applying +3.5 kOe parallel to the remnant magnetization and −3.5 kOe antiparallel to the remnant magnetization shifts the resonance frequency at 201 GHz in 1 by +6 and −4 GHz and that in 2 by +4 and −4 GHz, respectively. Simulations of the ferromagnetic resonance using the Landau−Lifshitz−Gilbert model reproduce the magnetic field‐induced shifts of the resonance frequencies. The 220 GHz band millimeter wave is the highest frequency with a high transparency for “atmospheric windows” and is expected to be a carrier frequency for sixth‐generation mobile communication systems (6 G) or 7 G. This study may help realize applications for millimeter‐wave isolators, circulators, or shutters.

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“…In 2014, the aggregate crystals in the hare's fur glaze were first confirmed as metastable epsiloniron oxide phase (ε-Fe 2 O 3 ) rather than the most thermally stabled hematite (α-Fe 2 O 3 ) [10]. ε-Fe 2 O 3 only existing in nanoparticles, nanorods, nanowires, or thin-film forms has recently received growing attention due to its significant and promising magnetic properties such as a giant coercive field of around 2T at room temperature, magneto-resistance, a millimeterwave ferromagnetic resonance (FMR) absorption [11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

A Microstructural and Compositional Study of ε-Fe2O3 Crystals in the Hare’s Fur Jian Ware

et al. 2022

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The Jian kilns in the present-day Jianyang County of Fujian Province are well known for their thick and lustrous black-glazed porcelain production. The hare’s fur (HF) glazed Jian wares characterized by radial fur-like strips, as one of the most typical representatives of black-glazed tea bowls, originate from phase separation of glaze melt and crystallization of iron oxides. In this study, various techniques were performed on the yellowish-brown HF samples, including portable energy-dispersive X-ray fluorescence (PXRF), synchrotron X-ray absorption near-edge spectroscopy (XANES), optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy (RS). The objective of this study was to well understand the microstructure characteristics and chemical compositions of glaze patterns. Results showed that the main constituents of the ceramic glaze were alumina (10.61–16.43 wt.%), silica (62.20–77.07 wt.%), calcium (3.85–6.97 wt.%), and iron oxide (4.10–8.35 wt.%). The studies provided evidence that metastable epsilon-iron oxide crystals (ε-Fe2O3) formed on the brownish-yellow glazed surface. Microstructural analysis revealed that there were three types of crystal structures in the glaze surface: One consisted of well-grown leaf-like or dendritic-like structure with highly ordered branches at micrometers scales; another comprised flower-like clusters accompanied by branches radiating from the center, petals growing along the branches, and needles on both sides of the petals; the last type involved a honeycomb structure tightly packed with plentiful spherical or irregular-shaped particles. In addition, ε-Fe2O3 crystals in the cross-section of the glaze showed a gradient distribution.

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Spin Seebeck effect in ɛ-Fe2O3 thin films with high coercive field

Cited by 14 publications

References 39 publications

Stabilization of ε−Fe2O3 epitaxial layer on MgO(111)/GaN via an intermediate γ -phase

Stabilization of ε−Fe2O3 epitaxial layer on MgO(111)/GaN via an intermediate γ -phase

Resonance Frequency Tuning of a 200 GHz Band Absorber by an External Magnetic Field

A Microstructural and Compositional Study of ε-Fe2O3 Crystals in the Hare’s Fur Jian Ware

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