Angle-Dependent<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msup><mml:mi>Ni</mml:mi><mml:mrow><mml:mn>2</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:math>X-Ray Magnetic Linear Dichroism: Interfacial Coupling Revisited

Arenholz, Elke; Laan, G. van der; Chopdekar, Rajesh V.; Suzuki, Yuri

doi:10.1103/physrevlett.98.197201

Cited by 103 publications

(83 citation statements)

References 22 publications

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“…Experimental and theoretical studies in the last decade [5,20,21,22,23,24,25] have demonstrated that MLD-XAS is a very powerful method to investigate thin film magnetic properties, especially as far as antiferromagnetic materials are concerned. To illustrate the application of this technique specifically for our case, we start with the XAS spectra for a 30 ML NiO/Ag film.…”

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confidence: 99%

Image charge screening: A new approach to enhance magnetic ordering temperatures in ultrathin correlated oxide films

Altieri¹,

Finazzi

Hsieh

et al. 2009

Phys. Rev. B

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We have tested the concept of image charge screening as a new approach to enhance magnetic ordering temperatures and superexchange interactions in ultra thin films. Using a 3 monolayer NiO(100) film grown on Ag(100) and an identically thin film on MgO(100) as model systems, we observed that the Néel temperature of the NiO film on the highly polarizable metal substrate is 390 K while that of the film on the poorly polarizable insulator substrate is below 40 K. This demonstrates that screening by highly polarizable media may point to a practical way towards designing strongly correlated oxide nanostructures with greatly improved magnetic properties.PACS numbers: 75.30.Et, 78.70.Dm Transition metal oxides exhibit many spectacular magnetic and electrical properties including high temperature superconductivity and colossal magnetoresistance [1] making them particularly promising for nanoscience technology applications. An acute issue in the field of nanoscience, however, is the strong reduction of the relevant critical or ordering temperatures due to well known finite size effects [2,3,4,5]. If ways could be found to compensate for these reductions, one would immediately enlarge the materials basis for nano-technology. Current approaches to overcome these problems include the use of chemical doping, pressure, and strain [6,7,8,9,10,11].Here we propose to exploit image charge screening as a new method to compensate finite size phenomena and to enhance magnetic ordering temperatures well beyond the capability of conventional methods [6,7,8,9,10,11]. The basic idea is to bring the material in the close proximity of a strongly polarizable medium. The relevant exchange and superexchange interactions, and thus the related magnetic ordering temperatures, can then be substantially amplified by reducing the energies of the underlying virtual charge excitations as a result of the image-charge-like screening by the polarizable medium [12,13,14].To prove this concept we have chosen to measure the Néel temperature T N of a 3 monolayer (ML) NiO film epitaxially grown on a MgO(100) substrate and of an equally thin film on Ag(100). NiO on MgO and on Ag are ideal model systems for this study because of their simple crystal structure and well characterized growth properties. They have a rock-salt crystal structure with lattice constant a M gO = 4.212Å and a N iO = 4.176Å, respectively, corresponding to a lattice misfit of about 1%. This ensures a perfect layer-by-layer epitaxial growth of NiO(100) on MgO(100), with a NiO(100) film surface roughness of about 0.1Å [15]. Silver has a cubic fcc structure with a lattice constant a Ag = 4.086Å and a mismatch with respect to NiO of about 2%. When misfit dislocations are avoided by keeping the film thickness below the critical thickness for strain relaxation (about 30 ML for NiO/Ag [16]) as done in the present work, then NiO(100) films grow on Ag(100) in a nicely layered and coherent mode with a sharp interface. This was already demonstrated by Kado [17,18], but it has also been verified ...

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confidence: 99%

Image charge screening: A new approach to enhance magnetic ordering temperatures in ultrathin correlated oxide films

Altieri¹,

Finazzi

Hsieh

et al. 2009

Phys. Rev. B

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“…In contrast, 3d systems with strong CEF interaction can quite often have I 0 + I 45 ≈ 0 [7,8]. This necessitates an interesting change in the spectral shape when going from weak to strong CEF interaction, since one would unlikely encounter that the XMLD signal disappears for intermediate CEF.…”

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“…Large anisotropic x-ray magnetic linear dichroism (AXMLD) at the L 2,3 x-ray absorption (XA) edge has been reported from 3d transition metal oxides [6][7][8]. It was shown that the angular dependence of the x-ray magnetic linear dichroism (XMLD) does not only depend on the orientations of the linear x-ray polarization, E, and the sample magnetization, H, but also on the relative orientation of these two vectors with respect to the crystallographic axes.…”

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confidence: 99%

Contribution of Eu 4f states to the magnetic anisotropy of EuO

Arenholz

Schmehl

Schlom

et al. 2009

Journal of Applied Physics

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Anisotropic x-ray magnetic linear dichroism (AXMLD) provides a novel element-, site-, shelland symmetry-selective technique to study the magnetic anisotropy induced by a crystalline electric field. The weak Eu 2+ M 4,5 AXMLD observed in EuO(001) indicates that the Eu 4f states are not rotationally invariant and hence contribute weakly to the magnetic anisotropy of EuO. The results are contrasted with those obtained for 3d transition metal oxides.

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“…The element-, site-, and valence-specificity of soft x ray dichroism techniques [6] allow a thorough characterization of magnetic interfaces elucidating the basic principles of magnetic coupling. Taking into account the recently discovered strong angular dependence of XMLD [7] we find that the Co moments are oriented perpendicular to the NiO moments. We emphasize the importance of the XMLD anisotropy on the intensity ratio of the two peaks at the Ni L 2 edge, that are often used to determine the spin orientation in antiferromagnets using XMLD [8][9][10].…”

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Magnetic structure near the Co∕NiO(001) interface

Arenholz

Laan

Nolting

2008

Applied Physics Letters

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We investigate the magnetic coupling at the Co/NiO interface using soft x-ray magnetic linear dichroism (XMLD) and circular dichroism taking explicitly into account the recently observed angular dependence of the XMLD with respect to the crystallographic axes. We find that the Co moments are aligned perpendicular to the NiO moments. We discuss the impact of the anisotropic XMLD on the intensity ratio of the two peaks at the Ni L 2 edge, which is commonly employed to determine the spin orientation in antiferromagnets using XMLD.

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Angle-DependentNi2+X-Ray Magnetic Linear Dichroism: Interfacial Coupling Revisited

Cited by 103 publications

References 22 publications

Image charge screening: A new approach to enhance magnetic ordering temperatures in ultrathin correlated oxide films

Image charge screening: A new approach to enhance magnetic ordering temperatures in ultrathin correlated oxide films

Contribution of Eu 4f states to the magnetic anisotropy of EuO

Magnetic structure near the Co∕NiO(001) interface

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