Spin-resolved photoemission investigation of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>c</mml:mi><mml:mo>(</mml:mo><mml:mn>2</mml:mn><mml:mn /><mml:mo>×</mml:mo><mml:mn>2</mml:mn><mml:mo>)</mml:mo></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>c</mml:mi><mml:mo>(</mml:mo><mml:mn>3</mml:mn><mml:mn /><mml:mo>×</mml:mo><mml:mn>1</mml:mn><mml:mo>)</mml:mo></mml:math>oxygen overlayers on the Fe(110) surface

Kim, H.-J.; Vescovo, E.

doi:10.1103/physrevb.58.14047

Cited by 21 publications

(15 citation statements)

References 11 publications

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“…25 The degree of crystalline order of the thin epitaxial Fe films used in our experiments has been checked by LEED. In agreement with previous studies 25,26 very sharp (1ϫ1) LEED patterns have been observed ͓Fig. 1͑a͔͒.…”

supporting

confidence: 92%

Evidence for the half-metallic ferromagnetic state ofFe3O4by spin-resolved photoelectron spectroscopy

2002

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The spin-dependent electronic structure of thin epitaxial films of magnetite, Fe 3 O 4 (111), has been investigated at room temperature by means of spin-, energy-, and angle-resolved photoemission spectroscopy. Near the Fermi energy E F a spin polarization of Ϫ(80Ϯ5)% is found. The spin-resolved photoemission spectra for binding energies between 1.5 eV and E F show good agreement with spin-split band energies from densityfunctional calculations.PACS number͑s͒: 75.70. Ak, 75.50.Bb, 75.70.Cn, 79.60.Bm The materials class of half-metallic ferromagnets ͑HMF's͒ has attracted renewed interest recently in the search for efficient spin polarizers in spin electronics.1 The intriguing feature of metallic conductivity for one spin component and semiconducting behavior for the other was in most cases theoretically predicted on the basis of electron band structure calculations. An experimental struggle extended over many years and is still ongoing to convincingly verify the truly intrinsic spin-dependent electronic structure of HMF's and consequently the high-spin polarization at the Fermi energy E F . The use of surface-sensitive measurements like spinpolarized photoemission, tunneling into superconductors, or superconducting point-contact spectroscopy imposed severe constraints in addition to problems with sample stoichiometry and homogeneity. In many cases the preparation of highquality thin films was indispensable instead of bulk single crystals which are believed to be superior. Thus, from the first theoretical prediction of, e.g., HMF behavior in Heusler alloys in 1983, 2 it took almost two decades to find evidence for spin polarization values at E F which come close to the expected ones.3 However, problems with the stoichiometry and especially surface composition of the films used are prevailing. [3][4][5] Besides the Heusler alloys, the majority of HMF's have been identified among transition metal oxides on the basis of the local spin-density approximation ͑LSDA͒ to the densityfunctional theory. Predictions have been made for Fe 3 O 4 , 6,7 CrO 2 , 8,9 manganites, 10,11 and the double perovskite Sr 2 FeMoO 6 .12 Only recently, values of the spin polarization of over 90% near E F were found for CrO 2 at 1.8 K using superconducting point-contact spectroscopy, 13,14 although values of 95% had been obtained earlier at 300 K at binding energies of 2 eV below E F using spin-polarized photoemission. 15 The most straightforward evidence of a minority spin gap and a concomitant 95% spin polarization near E F was obtained in La 0.7 Sr 0.3 MnO 3 at 40 K by means of spin-polarized photoemission spectroscopy. 16In this paper we present experimental evidence for the half-metallic ferromagnetic state of magnetite (Fe 3 O 4 ) by means of spin-and angle-resolved vacuum ultraviolet ͑VUV, hϭ21.2 eV͒ photoemission spectroscopy. Using epitaxial Fe 3 O 4 (111) films we obtain at room temperature a negative spin polarization of Ϫ(80Ϯ5)% at E F . This value agrees within 6% with the magnetization at 300 K of a thin Fe 3 O 4 film. 17 M...

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supporting

confidence: 92%

Evidence for the half-metallic ferromagnetic state ofFe3O4by spin-resolved photoelectron spectroscopy

2002

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“…2 is identical to that produced by the c(2ϫ2) oxygen reconstructed Fe͑110͒ surface. 26,27 Atomically resolved STM data of that surface have also revealed a structure which is almost identical to that shown in Fig. 2͑d͒, including antiphase domain boundaries like the one shown in Fig.…”

Section: Resultssupporting

confidence: 63%

“…A similar LEED pattern is commonly observed on the Fe͑110͒ surface, upon the adsorption of 0.25 ML of O 2 . 26,27 In this case, the pattern is identified as a c(2ϫ2) reconstruction, with respect to the nonprimitive unit cell of the surface.…”

Section: Methodsmentioning

confidence: 99%

Layer-dependent reactivity in the Fe/Mo(110) epitaxial ultrathin film system

et al. 2003

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Fe films in the 0.4рр4.7 ML ͑monolayer͒ coverage range were deposited on a Mo͑110͒ substrate at temperatures between 300 K and 700 K, under ultrahigh vacuum conditions. The adsorption of CO, CO 2 , H 2 O, and O 2 onto these films from the residual gas within the Ultrahigh vacuum system has been studied using scanning tunneling microscopy, low-energy electron diffraction, and Auger electron spectroscopy analysis. The first, second, and third Fe layers display distinct structures, correlated to the different adsorption characteristics of each layer. Separate mechanisms are identified as the cause of this layer-dependent reactivity. The difference between the first and second Fe layers is attributed to the difference in charge polarization effected between these layers and the substrate. However, our results prove that the different adsorption characteristics of the pseudomorphically strained first layer and the two-dimensionally strain-relieved third layer are directly linked to the film strain.

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“…3 (a)) show the emission from the 1 ↓ ⊕ 3 ↓ states near 0.25 eV and from the 1 ↑ ⊕ 4 ↑ states near 0.7 eV. The spectra are in agreement with previous measurements [66,67]. The Fe(110) films show a spin-polarization value of about −(80 ± 5)% at E F at 293 K. The spin-resolved spectra of the valence band near E F clearly show a dominant emission from the minority Fe-3d states (≤1.5 eV) (Fig.…”

Section: Magnetitesupporting

confidence: 90%

Growth and Room Temperature Spin Polarization of Half-metallic Epitaxial CrO2 and Fe3O4 Thin Films

Fonin¹,

Dedkov²,

Rüdiger³

et al. 2005

Local-Moment Ferromagnets

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Abstract. Potential applications of systems based on half-metallic ferromagnets (HMFs) in magneto-and spinelectronics including spin injectors, magnetic field sensors and magnetic memory devices stimulated the investigation of the electronic properties of HFMs by a multitude of experimental and theoretical approaches. The main question remains however if the 100% spin polarization at the Fermi level (EF) theoretically predicted for HFMs can be confirmed experimentally. This article gives a short overview on the half-metallic ferromagnets with special emphasis on magnetite (Fe3O4) and chromium dioxide (CrO2). The spin-resolved electronic structure of thin epitaxial Fe3O4(111) and CrO2(100) films has been investigated at 293 K by means of spin-resolved photoemission spectroscopy (SP-PES). Epitaxial Fe3O4(111) films have been grown on different substrates by oxidizing epitaxial Fe(110) films. High surface quality and chemical homogeneity as well as high crystalline order in the bulk of Fe3O4(111) films were confirmed by means of STM and LEED. The Fe3O4(111) epitaxial films show a maximum spin polarization value of −(80±5)% near EF at 293 K confirming the half-metallic nature of Fe3O4 in the [111] direction. High-quality epitaxial CrO2(100) films have been prepared by a chemical vapor deposition technique. Near EF an energy gap was observed for spin-down electrons and a spin polarization of about +(90 ± 10)% was found at 293 K by means of SP-PES. This value and the magnitude of the gap in the minority spin channel are in good agreement with the prediction of the half-metallic nature of CrO2.

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Spin-resolved photoemission investigation of thec(2×2)andc(3×1)oxygen overlayers on the Fe(110) surface

Cited by 21 publications

References 11 publications

Evidence for the half-metallic ferromagnetic state ofFe3O4by spin-resolved photoelectron spectroscopy

Evidence for the half-metallic ferromagnetic state ofFe3O4by spin-resolved photoelectron spectroscopy

Layer-dependent reactivity in the Fe/Mo(110) epitaxial ultrathin film system

Growth and Room Temperature Spin Polarization of Half-metallic Epitaxial CrO2 and Fe3O4 Thin Films

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