Structural and magnetic properties of magnetite-containing epitaxial iron oxide films grown on MgO(001) substrates

Kado, Tetsuo

doi:10.1063/1.2840118

Cited by 19 publications

(9 citation statements)

References 25 publications

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“…Figure 6 shows the (ZFC) magnetization curves obtained during heating for the series of 20 nm films grown at the indicated oxygen pressures. A sharp Verwey transition was found at 121 K, close to the bulk value [31], in of the all films except the two grown under 1 × 10 −6 and 4 × 10 -6 torr oxygen pressure. However, the magnitude of Verwey transition decreases significantly as the oxygen pressure is decreased from 7 × 10 -7 to 5 × 10 -7 torr, and then 3 × 10 -7 torr.…”

Section: Magnetizationsupporting

confidence: 67%

Structural phase diagram for ultra-thin epitaxial Fe₃O₄ / MgO(0 0 1) films: thickness and oxygen pressure dependence

Alraddadi¹,

Hines²,

Yilmaz³

et al. 2016

J. Phys.: Condens. Matter

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A systematic investigation of the thickness and oxygen pressure dependence for the structural properties of ultra-thin epitaxial magnetite (Fe3O4) films has been carried out; for such films, the structural properties generally differ from those for the bulk when the thickness ⩽10 nm. Iron oxide ultra-thin films with thicknesses varying from 3 nm to 20 nm were grown on MgO (0 0 1) substrates using molecular beam epitaxy under different oxygen pressures ranging from 1 × 10(-7) torr to 1 × 10(-5) torr. The crystallographic and electronic structures of the films were characterized using low energy electron diffraction (LEED) and x-ray photoemission spectroscopy (XPS), respectively. The quality of the epitaxial Fe3O4 ultra-thin films was judged by magnetic measurements of the Verwey transition, along with complementary XPS spectra. It was observed that under the same growth conditions the stoichiometry of ultra-thin films under 10 nm transforms from the Fe3O4 phase to the FeO phase. In this work, a phase diagram based on thickness and oxygen pressure has been constructed to explain the structural phase transformation. It was found that high-quality magnetite films with thicknesses ⩽20 nm formed within a narrow range of oxygen pressure. An optimal and controlled growth process is a crucial requirement for the accurate study of the magnetic and electronic properties for ultra-thin Fe3O4 films. Furthermore, these results are significant because they may indicate a general trend in the growth of other oxide films, which has not been previously observed or considered.

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Section: Magnetizationsupporting

confidence: 67%

Structural phase diagram for ultra-thin epitaxial Fe₃O₄ / MgO(0 0 1) films: thickness and oxygen pressure dependence

Alraddadi¹,

Hines²,

Yilmaz³

et al. 2016

J. Phys.: Condens. Matter

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“…2͒ and its characteristic metal-insulator transition at 120 K ͑Verwey transition͒. [3][4][5] Differences between some properties of bulk magnetite and epitaxial thin films have been observed, such as an increased resistivity with decreasing film thickness, [6][7][8] negative magnetoresistance, [9][10][11] decreased and broadened Verwey transition temperature ͑T V ͒, 7,12,13 superparamagnetism in ultrathin films, 14,15 decreased saturation magnetization, [16][17][18][19] and anomalous, planar, and ordinary Hall effects. [20][21][22] This anomalous behavior has often been associated to the film microstructure and the presence of structural growth defects called antiphase boundaries ͑APBs͒.…”

Section: Introductionmentioning

confidence: 99%

Origin of the giant magnetic moment in epitaxialFe3O4thin films

et al. 2010

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We study the enhanced magnetic moment observed in epitaxial magnetite ͑Fe 3 O 4 ͒ ultrathin films ͑t Ͻ 15 nm͒ grown on MgO ͑001͒ substrates by means of pulsed laser deposition. The Fe 3 O 4 ͑001͒ thin films exhibit high crystallinity, low roughness, and sharp interfaces with the substrate, and the existence of the Verwey transition at thicknesses down to 4 nm. The evolution of the Verwey transition temperature with film thickness shows a dependence with the antiphase boundaries density. Superconducting quantum interference device ͑SQUID͒ and vibrating sample magnetometry measurements in ultrathin films show a magnetic moment much higher than the bulk magnetite value. In order to study the origin of this anomalous magnetic moment, polarized neutron reflectivity ͑PNR͒, and x-ray magnetic circular dichroism ͑XMCD͒ experiments have been performed, indicating a decrease in the magnetization with decreasing sample thickness. X-ray photoemission spectroscopy measurements show no metallic Fe clusters present in the magnetite thin films. Through inductively coupled plasma mass spectroscopy and SQUID magnetometry measurements performed in commercial MgO ͑001͒ substrates, the presence of Fe impurities embedded within the substrates has been observed. Once the substrate contribution has been corrected, a decrease in the magnetic moment of magnetite thin films with decreasing thickness is found, in good agreement with the PNR and XMCD measurements. Our experiments suggest that the origin of the enhanced magnetic moment is not intrinsic to magnetite but due to the presence of Fe impurities in the MgO substrates.

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“…It has been reported that the Fe 3 O 4 films grow on MgO (100) coherently strained, relaxing partially above a critical thickness, but even for thickness of 700 nm the relaxation is still partial [120,129]. It has been observed that differences exist between some properties of the bulk material and those of epitaxial magnetite films, such as the non saturation of the magnetization at high fields [129,130], decreased and broadened Verwey transition temperature [124,127,128], superparamagnetic behavior of films below 5 nm [131,132], increased resistivity found in epitaxial magnetite films [119,124,133] and large negative magnetoresistance [134][135][136].…”

Section: Structure and Properties Of Epitaxial Fe 3 O 4 Filmsmentioning

confidence: 99%

Epitaxial Growth of half-metallic oxide thin Films by Pulsed Laser Depositions.

Esteban¹,

Juliá²

2010

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Structural and magnetic properties of magnetite-containing epitaxial iron oxide films grown on MgO(001) substrates

Cited by 19 publications

References 25 publications

Structural phase diagram for ultra-thin epitaxial Fe₃O₄ / MgO(0 0 1) films: thickness and oxygen pressure dependence

Structural phase diagram for ultra-thin epitaxial Fe₃O₄ / MgO(0 0 1) films: thickness and oxygen pressure dependence

Origin of the giant magnetic moment in epitaxialFe3O4thin films

Epitaxial Growth of half-metallic oxide thin Films by Pulsed Laser Depositions.

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Structural and magnetic properties of magnetite-containing epitaxial iron oxide films grown on MgO(001) substrates

Cited by 19 publications

References 25 publications

Structural phase diagram for ultra-thin epitaxial Fe3O4 / MgO(0 0 1) films: thickness and oxygen pressure dependence

Structural phase diagram for ultra-thin epitaxial Fe3O4 / MgO(0 0 1) films: thickness and oxygen pressure dependence

Origin of the giant magnetic moment in epitaxialFe3O4thin films

Epitaxial Growth of half-metallic oxide thin Films by Pulsed Laser Depositions.

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Product

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Structural phase diagram for ultra-thin epitaxial Fe₃O₄ / MgO(0 0 1) films: thickness and oxygen pressure dependence

Structural phase diagram for ultra-thin epitaxial Fe₃O₄ / MgO(0 0 1) films: thickness and oxygen pressure dependence