Enhanced Orbital Magnetism in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>Fe</mml:mi><mml:mn>50</mml:mn></mml:msub><mml:msub><mml:mi>Pt</mml:mi><mml:mn>50</mml:mn></mml:msub></mml:math>Nanoparticles

Antoniak, C.; Lindner, J.; Spasova, Marina; Sudfeld, D.; Acet, Mehmet; Farle, Michael; Fauth, K.; Wiedwald, Ulf; Boyen, Hans‐Gerd; Ziemann, P.; Wilhelm, F.; Рогалев, А.; Sun, Shouheng

doi:10.1103/physrevlett.97.117201

Cited by 156 publications

(117 citation statements)

References 34 publications

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“…6 for comparison. Although the Co K edge XAS calculated in Co 3 Co is only slightly different than Co 3 W at the pre-edge feature, the Co 3 Co XMCD is not split into two negative peaks, but closely resembles the bulk Co XMCD, which is similar to the measurement recorded in the Al 2 O 3 capped Co NPs [see Fig. 2(a)].…”

Section: B Co K Edgesupporting

confidence: 75%

“…It is then an important tool to study the magnetic anisotropy of these nanoparticles systems, e.g., to evaluate the contribution of the orbital moment to this anisotropy as a result of the symmetry breaking at the particle surface. 1,[3][4][5][6][7][8] However, not all magnetic nanoparticles have their anisotropy originated on surface effects. In particular, among the specific group of magnetic nanoparticles with amorphous structure, the amorphous Co-W alloy NPs constitute a paradigmatic example, where their anisotropy is not due to surface effects but results from the structural short range order (SRO) detected in the particles.…”

Section: Introductionmentioning

confidence: 99%

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Breakdown of Hund's third rule in amorphous Co-W nanoparticles and crystalline Co3W alloys

Figueroa

Bartolomé

et al. 2012

Phys. Rev. B

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We present x-ray absorption near edge structure (XANES) and x-ray magnetic circular dichroism (XMCD) measurements performed at the Co K and W L 2,3 edges, on amorphous Co-W alloy nanoparticles, and a comparison with those on a bulk Co 3 W alloy. A strong hybridization between the 4p and 3d orbitals in Co and the 5d band in W are observed, resulting in an induced magnetic moment in the W atoms. The orbital to spin moment ratio in W of all these Co-W systems is positive, suggesting a parallel orientation of the two moments. This is opposite to the expected antiparallel coupling for atoms with a less-than-half-filled 5d band, according to Hund's third rule. These findings are supported by calculations of the electronic density of states projected at the Co 3d and W 5d orbitals, as well as XANES spectra and XMCD signals at the Co K and W L 2,3 edges in a Co 3 W system.

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Section: B Co K Edgesupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

Breakdown of Hund's third rule in amorphous Co-W nanoparticles and crystalline Co3W alloys

Figueroa

Bartolomé

et al. 2012

Phys. Rev. B

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“…3͒. The lower Fe atomic magnetic moment observed in the Pt capping case when compared to the Pd capping case is consistent with the fact that in general, the Fe atomic moment is lower in FePt alloys [22][23][24] than in FePd alloys. 25,26 Furthermore, this is particularly true for FePt and FePd disordered alloys 22,25,26 that form at low temperatures, which is likely to be the case here since the capping layers were deposited at room temperature ͑RT͒ ͑the ordered FePt and FePd alloys form at elevated temperatures͒.…”

Section: X-ray Magnetic Circular Dichroism: Interface Atomic Magnesupporting

confidence: 72%

Interface alloying effects in the magnetic properties of Fe nanoislands capped with different materials

et al. 2008

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We show that Fe nanoislands capped with Al, Pd, and Pt protecting layers include an alloy at the interface with the capping layer, which explains the previously known capping layer dependence on the interparticle magnetic coupling. Vibrating sample magnetometry results, for instance, are evidencing a reduction in the magnetization measured under a magnetic field of 15 mT, which is larger in the case of the Al capping and which is due to the presence of a magnetically dead interface alloy. This reduction is also observed at the atomic level using x-ray magnetic circular dichroism measurements, showing a capping layer dependence of the Fe magnetic-moment reduction that is similar for the Pd and Pt capping, and stronger for the Al capping. The trend in the magnetic properties as a function of the capping layer is explained in the light of x-ray photoemission spectroscopy results that evidence the formation of alloys at the interface between the Fe nanoislands and the capping layers. The present results highlight the strong influence of interface alloying in systems of reduced dimensionality. In particular, it is shown that the magnetic properties are strongly affected at both the atomic and macroscopic level.

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“…Note that the values taken from ref. 30 have been recalculated with the same number of unoccupied d-states. As predicted by theory, the magnetic moments at the Fe sites of Al-capped FePt particles with diameters around 6 nm are significantly reduced with respect to the ones of uncapped nanoparticles of the same size 30 .…”

Section: Resultsmentioning

confidence: 99%

A guideline for atomistic design and understanding of ultrahard nanomagnets

et al. 2011

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magnetic nanoparticles are of immense current interest because of their possible use in biomedical and technological applications. Here we demonstrate that the large magnetic anisotropy of FePt nanoparticles can be significantly modified by surface design. We employ X-ray absorption spectroscopy offering an element-specific approach to magnetocrystalline anisotropy and the orbital magnetism. Experimental results on oxide-free FePt nanoparticles embedded in Al are compared with large-scale density functional theory calculations of the geometric-and spin-resolved electronic structure, which only recently have become possible on world-leading supercomputer architectures. The combination of both approaches yields a more detailed understanding that may open new ways for a microscopic design of magnetic nanoparticles and allows us to present three rules to achieve desired magnetic properties. In addition, concrete suggestions of capping materials for FePt nanoparticles are given for tailoring both magnetocrystalline anisotropy and magnetic moments.

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Enhanced Orbital Magnetism inFe50Pt50Nanoparticles

Cited by 156 publications

References 34 publications

Breakdown of Hund's third rule in amorphous Co-W nanoparticles and crystalline Co3W alloys

Breakdown of Hund's third rule in amorphous Co-W nanoparticles and crystalline Co3W alloys

Interface alloying effects in the magnetic properties of Fe nanoislands capped with different materials

A guideline for atomistic design and understanding of ultrahard nanomagnets

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