Temperature-dependent spectral generalized magneto-optical ellipsometry for ferromagnetic compounds

Rauer, R.; Neuber, G.; Kunze, Jörg; Bäckström, Joakim; Rübhausen, Michael

doi:10.1063/1.1834702

Cited by 42 publications

(26 citation statements)

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“…The off-diagonal components of the dielectric tensor are calculated from many ␦I / I measurements for different polarizer and analyzer orientations. 8 Thus, ␦I / I shows a similar temperature dependence for both planes ͓Fig. 4͔.…”

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confidence: 58%

“…8 Standard ellipsometry was performed for temperatures from 10 to 470 K in the spectral range from 0.5 to 5.5 eV. In SGME, one measures the fractional difference of the intensities of light at a particular polarization angle for magnetic fields, which is applied along opposite directions, i.e., ␦I / I 8,9 A magnetic field H = Ϯ 440 mT was applied parallel to the normal vector of the plane of incidence. SGME measurements were performed in the spectral range from 1.6 to 5.5 eV for temperatures from 15 to 300 K. For measurements on the BC plane, two identical lenses were mounted in order to reduce the spot size to 100 ϫ 300 m 2 .…”

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confidence: 99%

“…The cryostat has stress-free mounted windows and maintains a base pressure of about 3 ϫ 10 −8 mbar at room temperature. 8 Standard ellipsometry was performed for temperatures from 10 to 470 K in the spectral range from 0.5 to 5.5 eV. In SGME, one measures the fractional difference of the intensities of light at a particular polarization angle for magnetic fields, which is applied along opposite directions, i.e., ␦I / I…”

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Magneto-optical study of the spin-polarized electronic states in multiferroicTbMnO3

et al. 2008

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The magnetic and electronic properties of multiferroic TbMnO 3 in the paramagnetic, antiferromagnetic, sinusoidal, and spiral-spin phases were studied by spectral generalized magneto-optical ellipsometry. The measurements show a strong anisotropy of the dielectric tensor. A redistribution of spectral weight was observed in the diagonal components of the dielectric tensor for the temperature range from 110 to T N =46 K. In the off-diagonal elements, spectral generalized magneto-optical ellipsometry shows sensitivity to the antiferromagnetic and ferroelectric phase transitions at T N = 46 K and T F = 29 K, respectively, and a persistent signal up to 6T N . DOI: 10.1103/PhysRevB.77.193105 PACS number͑s͒: 75.47.Lx, 75.25.ϩz, 75.50.Ee, 77.22.Ej Multiferroic materials exhibit phases with simultaneous magnetic and ferroelectric properties. The close coupling of the magnetization and the electric polarization in multiferroics makes these materials excellent candidates for demonstrating giant magnetoelectrical behavior, 1,2 in which large magnetic and electric responses can be induced with weak electric and magnetic fields, respectively. 3,4 Spectral generalized magneto-optical ellipsometry ͑SGME͒ is an ideal technique for studying the interplay between electric and magnetic properties in multiferroic systems, as it probes both the diagonal xx and off-diagonal xy components of the dielectric tensor. 5 Multiferroicity in TbMnO 3 is induced by spin-charge coupling. Below the Néel temperature T N = 46 K, the wavelength of the incommensurate spin density decreases with decreasing temperature down to the ferroelectric transition at T F = 29 K. In the absence of a magnetic field, this spin-density modulation gets locked in at T F . Below T F , the inversion symmetry of the lattice is broken by the bc-cycloidal arrangement of the spins, inducing a ferroelectric polarization along the c axis while the antiferromagnetic ordering along the b axis persists. 3,4,6 Here, we study the coupling between spin and charge degrees of freedom in multiferroic TbMnO 3 by examining the temperature-dependent dielectric responses xx and xy , which are the diagonal and off-diagonal components of the dielectric tensor. The magnetization of a material breaks the symmetry between left and right circularly polarized ͑LCP and RCP͒ light. While 2xx is proportional to the sum of absorptions of LCP and RCP light, 1xy is proportional to the difference. 7 Consequently, a complete magneto-optical characterization of 2xx and 1xy in a magnetic material provides detailed information regarding the coupling between the material's electronic and magnetic properties.The temperature-dependent ellipsometry was done with a custom-made setup by using an extended Sentech SE850 spectral ellipsometer inside a He flow cryostat. The cryostat has stress-free mounted windows and maintains a base pressure of about 3 ϫ 10 −8 mbar at room temperature. 8 Standard ellipsometry was performed for temperatures from 10 to 470 K in the spectral range from 0.5 to 5.5 eV. In SGME, on...

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Magneto-optical study of the spin-polarized electronic states in multiferroicTbMnO3

et al. 2008

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“…It covered an energy range from 0.5 to 5.5 eV, and was equipped with an ultra-high-vacuum cryostat. For spectral generalized magneto-optical ellipsometry (SGME), additional mounted Helmholtz coils enable the application of a fast-switching external magnetic field of 4500 Oe in transverse magneto-optical Kerr effect (TMOKE) geometry [38]. As the penetration depth was above 200 nm in this energy range, the whole film was scanned optically.…”

Section: (B) Magnetic Propertiesmentioning

confidence: 99%

Cationic-vacancy-induced room-temperature ferromagnetism in transparent, conducting anatase Ti _{1−
x} Ta _x O ₂ ( x ∼0.05) thin films

Rusydi

Dhar

Barman

et al. 2012

Phil. Trans. R. Soc. A.

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We report room-temperature ferromagnetism (FM) in highly conducting, transparent anatase Ti 1−x Ta x O 2 (x ∼ 0.05) thin films grown by pulsed laser deposition on LaAlO 3 substrates. Rutherford backscattering spectrometry (RBS), X-ray diffraction, protoninduced X-ray emission, X-ray absorption spectroscopy (XAS) and time-of-flight secondary-ion mass spectrometry indicated negligible magnetic contaminants in the films. The presence of FM with concomitant large carrier densities was determined by a combination of superconducting quantum interference device magnetometry, * Authors for correspondence (phyandri@nus.edu.sg; eleds@nus.edu.sg; venky@nus.edu.sg). † These authors contributed equally to this work. electrical transport measurements, soft X-ray magnetic circular dichroism (SXMCD), XAS and optical magnetic circular dichroism, and was supported by first-principles calculations. SXMCD and XAS measurements revealed a 90 per cent contribution to FM from the Ti ions, and a 10 per cent contribution from the O ions. RBS/channelling measurements show complete Ta substitution in the Ti sites, though carrier activation was only 50 per cent at 5 per cent Ta concentration, implying compensation by cationic defects. The role of the Ti vacancy (V Ti ) and Ti 3+ was studied via XAS and X-ray photoemission spectroscopy, respectively. It was found that, in films with strong FM, the V Ti signal was strong while the Ti 3+ signal was absent. We propose (in the absence of any obvious exchange mechanisms) that the localized magnetic moments, V Ti sites, are ferromagnetically ordered by itinerant carriers. Cationic-defect-induced magnetism is an alternative route to FM in wide-band-gap semiconducting oxides without any magnetic elements.

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“…8 The optical absorption of various graphene layers was measured using a spectroscopic generalized ellipsometer (SGE). 9 The experiments were conducted under an ultra-high vacuum condition of 5x10 -9 mbar in order to ensure that there was no surface contamination during the measurements. The SGE is a unique spectroscopic technique because, from one single measurement, the dielectric function (i*ε 1 + ε 2 ) as well as the absorption coefficient can be obtained without performing the Kramers-Kronig transformation.…”

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confidence: 99%

A new route to graphene layers by selective laser ablation

Dhar

Barman

et al. 2011

AIP Advances

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Selectively creating regions of spatially varying thickness may enable the utilization of the electronic properties of N-layer (N=1 or more) graphene and other similar layered materials (e.g., topological insulators or layered superconductors) for novel devices and functionalities on a single chip. The ablation threshold energy density increases dramatically for decreasing layer numbers of graphene originating from the dimensional crossover of the specific heat. For the 2D regime of graphite (up to N≈7) the dominant flexural mode specific heat (due to its N-1 dependence) gives rise to a strong layer number-dependence on the pulsed laser ablation threshold energy density, while for 3D regime (N>>7) the ablation threshold saturates due to dominant acoustic mode specific heat. As a result, several energy density windows exist between the minimum energy densities that are required for ablating single, bi, or more layers of graphene, allowing layer number selectivity

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Temperature-dependent spectral generalized magneto-optical ellipsometry for ferromagnetic compounds

Cited by 42 publications

References 9 publications

Magneto-optical study of the spin-polarized electronic states in multiferroicTbMnO3

Magneto-optical study of the spin-polarized electronic states in multiferroicTbMnO3

Cationic-vacancy-induced room-temperature ferromagnetism in transparent, conducting anatase Ti _{1−
x} Ta _x O ₂ ( x ∼0.05) thin films

A new route to graphene layers by selective laser ablation

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Temperature-dependent spectral generalized magneto-optical ellipsometry for ferromagnetic compounds

Cited by 42 publications

References 9 publications

Magneto-optical study of the spin-polarized electronic states in multiferroicTbMnO3

Magneto-optical study of the spin-polarized electronic states in multiferroicTbMnO3

Cationic-vacancy-induced room-temperature ferromagnetism in transparent, conducting anatase Ti 1− x Ta x O 2 ( x ∼0.05) thin films

A new route to graphene layers by selective laser ablation

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Cationic-vacancy-induced room-temperature ferromagnetism in transparent, conducting anatase Ti _{1−
x} Ta _x O ₂ ( x ∼0.05) thin films