Doubling of the orbital magnetic moment in nanoscale Fe clusters

Edmonds, K. W.; Binns, C.; Baker, Salah A.; Thornton, S. C.; Norris, C.; Goedkoop, J.B.; Finazzi, Marco; Brookes, N. B.

doi:10.1103/physrevb.60.472

Cited by 140 publications

(95 citation statements)

References 22 publications

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“…On the other hand, the spin-orbit coupling splits the CF spin degenerate levels and a nonzero orbital moment contribution appears in the magnetic ground state. Usually the orbital moment is small compared to the spin component, but a remarkable enhancement of the orbital moment of magnetic systems was observed at film interfaces, 5 monoatomic metal chains, 6 nanoparticles, 7 or very small clusters. 8 In the limit of atomic size, that is, as atomic impurities in solids, the orbital moment may be only partially quenched, with values approaching the free atom ones.…”

Section: Introductionmentioning

confidence: 99%

Highly unquenched orbital moment in textured Fe-phthalocyanine thin films

et al. 2010

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X-ray magnetic circular dichroism ͑XMCD͒ measured at T = 6 K and 0 H = 5 T on the ␣-phase Fephthalocyanine ͑FePc͒ textured thin films shows that the Fe 2+ ions present an unusually large, highly unquenched m L = 0.53Ϯ 0.04 B orbital component, with planar anisotropy. The spin m S = 0.64Ϯ 0.05 B and the intra-atomic magnetic dipolar m T components were also obtained. The m L / m S = 0.83 ratio is the largest measured in 3d complexes and compounds. The origin of this unusually high orbital moment is the incompletely filled e g level lying close to the Fermi energy. This explains the unusually large and positive hyperfine field detected by Mössbauer spectroscopy in FePc. The FePc film strong planar anisotropy inferred from XMCD experiments is fully confirmed by magnetization measurements.

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Section: Introductionmentioning

confidence: 99%

Highly unquenched orbital moment in textured Fe-phthalocyanine thin films

et al. 2010

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“…In recent years, extensive work [10][11][12][13][14][15][16][17][18][19] on magnetic surfaces and thin films has shown that a lowering of the symmetry results in an increase of m L compared to bulk systems, where the d-state hybridization and the crystal field effectively quench m L . This effect gives rise to a variety of interesting phenomena, such as enhanced and perpendicular magnetic anisotropy [2,[12][13][14][15][16]19].…”

Section: Introductionmentioning

confidence: 99%

Magnetic anisotropy from single atoms to large monodomain islands of Co/Pt(111)

Gambardella

Rusponi

Cren

et al. 2005

Comptes Rendus. Physique

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By studying the magnetic behavior of self-assembled Co islands on a single-crystal metal surface, Pt(111), we show how the magnetic anisotropy evolves from isolated atoms to monolayer islands and films. Single Co adatoms are found to have a giant magnetocrystalline anisotropy energy of E a = 9.3 ± 1.6 meV/atom arising from the combination of partly preserved orbital moments (m L = 1.1 µ B ) and strong spin-orbit coupling induced by the Pt substrate. Combined scanning tunneling microscopy and X-ray magnetic circular dichroism experiments performed for differently sized small two-dimensional Co islands establish a clear connection between E a and m L , both quantities decrease sharply with the lateral coordination of the magnetic atoms. In accordance with this, Kerr magnetometry experiments, again performed in conjunction with scanning tunneling microscopy, reveal that the anisotropy energy of large two-dimensional Co islands is almost entirely determined by the relatively low number of perimeter atoms, having E a = 0.9 ± 0.1 meV/atom. These results confirm theoretical predictions and are of fundamental value the understanding of how the magnetic anisotropy develops in finite-size magnetic particles. Identification of the role of perimeter and surface atoms opens up new opportunities for engineering the anisotropy and the moment of a magnetic nanostructure. RésuméAnisotropie magnétique de l'atome isolé aux îlots monocouches de Co/Pt(111). En étudiant les propriétés magnétiques de particules de Co auto assemblées sur une surface d'orientation (111) d'un monocristal de Pt, nous montrons comment l'anisotropie magnétique évolue de l'atome isolé aux îlots monocouches et aux films ultraminces. Nous trouvons que les atomes de Co isolés adsorbés en surface ont une énergie d'anisotropie magnétocrystalline de E a = 9.3 ± 1.6 meV/atome provenant de la combinaison d'un moment orbital conservé (m L = 1.1 µ B ) et d'un fort couplage spin-orbite induit par le substrat de Pt. Des expériences combinées de microscopie à effet tunnel et de dichroïsme circulaire magnétique à rayons X, effectués sur des îlots de Co de petit taille établissent une connexion claire entre E a et m L , chacune de ces quantités décroissant rapidement avec la coordination latérale des atomes magnétiques. En conformité avec ceci, nous trouvons en employant la magnétométrie par effet Kerr et le microscope à effet tunnel que l'énergie d'anisotropie de grands îlots bidimensionnels de Co est presque entiè-rement déterminée par le nombre relativement faible d'atomes au périmètre, ayant E a = 0.9 ± 0.1 meV/atome. Ces résultats confirment les prédictions théoriques et sont d'un intérêt fondamental pour comprendre comment l'anisotropie magnétique se développe dans les particules magnétiques de taille finie. L'identification du rôle des atomes au périmètre et des atomes de surface ouvre de nouvelles opportunités pour l'ingénierie de l'anisotropie et du moment de nanostructures magnétiques. Pour citer cet article : P. Gambardella et al., C. R. Physique 6 (200...

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“…8,9 This excess was recently correlated to the augmentation of the orbital magnetic moment of the peripheral atoms. 10,11 Magnetic nanoparticles are also good candidates for the study of quantum effects in intermediate scales between the microscopic and the macroscopic classical world. 12,13 In real systems however, we usually deal with macroscopic ensembles of particles with different sizes and shapes.…”

Section: Introductionmentioning

confidence: 99%

Enhancement of the magnetic anisotropy of nanometer-sized Co clusters: Influence of the surface and of interparticle interactions

et al. 2002

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We study the magnetic properties of spherical Co clusters with diameters between 0.8 nm and 5.4 nm (25 to 7500 atoms) prepared by sequential sputtering of Co and Al2O3. The particle size distribution has been determined from the equilibrium susceptibility and magnetization data and it is compared to previous structural characterizations. The distribution of activation energies was independently obtained from a scaling plot of the ac susceptibility. Combining these two distributions we have accurately determined the effective anisotropy constant K ef f . We find that K ef f is enhanced with respect to the bulk value and that it is dominated by a strong anisotropy induced at the surface of the clusters. Interactions between the magnetic moments of adjacent layers are shown to increase the effective activation energy barrier for the reversal of the magnetic moments. Finally, this reversal is shown to proceed classically down to the lowest temperature investigated (1.8 K).

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Doubling of the orbital magnetic moment in nanoscale Fe clusters

Cited by 140 publications

References 22 publications

Highly unquenched orbital moment in textured Fe-phthalocyanine thin films

Highly unquenched orbital moment in textured Fe-phthalocyanine thin films

Magnetic anisotropy from single atoms to large monodomain islands of Co/Pt(111)

Enhancement of the magnetic anisotropy of nanometer-sized Co clusters: Influence of the surface and of interparticle interactions

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