The low field susceptibility of a textured superparamagnetic system

Chantrell, R.W.; Ayoub, N.Y.; Popplewell, J.

doi:10.1016/0304-8853(85)90150-7

Cited by 55 publications

(33 citation statements)

References 7 publications

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“…4) has been calculated by Chantrell et al [39], and given in the following form by Fruchart et al [40]: Fig. 4 shows that our analytical solution for χ(T ) (thick line) perfectly reproduces the numerical one.…”

Section: Temperature Dependence Of the Zero Field Susceptibility Of Asupporting

confidence: 58%

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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Section: Temperature Dependence Of the Zero Field Susceptibility Of Asupporting

confidence: 58%

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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“…25 As Fig. 5 shows, the in-phase susceptibility of sample TXT is larger than that of sample RDM above the blocking temperature but below the melting point.…”

Section: A Control Of Magnetic Texturementioning

confidence: 93%

Texture-induced magnetic interactions in ferrofluids

Urtizberea

Arizaga

Silva

et al. 2012

Journal of Applied Physics

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We report a method for reversibly controlling the strength of dipole-dipole interactions in maghemite ferrofluids. In order to induce some magnetic texture, the ferrofluid is exposed to a strong magnetic field while it is cooled from room temperature to below its freezing temperature. The experimental data show that the average strength of dipolar interactions increases with increasing texture and that the magnetic relaxation becomes slower. V C 2012 American Institute of Physics. [http://dx

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“…For particles oriented at an angle , m(H,T) is simply given by the average of the projection of the magnetic moment of the particles onto the field direction over all their possible orientations . In our model, this is 27,28 m͑H,T, ͒ϭ 1…”

Section: Two-state Approximationmentioning

confidence: 99%

Magnetic field scaling of relaxation curves in small particle systems

Iglesias

Labarta

2002

Journal of Applied Physics

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We study the effects of the magnetic field on the relaxation of the magnetization of small monodomain noninteracting particles with random orientations and distribution of anisotropy constants. Starting from a master equation, we build up an expression for the time dependence of the magnetization which takes into account thermal activation only over barriers separating energy minima, which, in our model, can be computed exactly from analytical expressions. Numerical calculations of the relaxation curves for different distribution widths, and under different magnetic fields H and temperatures T, have been performed. We show how a T ln(t/ 0 ) scaling of the curves, at different T and for a given H, can be carried out after proper normalization of the data to the equilibrium magnetization. The resulting master curves are shown to be closely related to what we call effective energy barrier distributions, which, in our model, can be computed exactly from analytical expressions. The concept of effective distribution serves us as a basis for finding a scaling variable to scale relaxation curves at different H and a given T, thus showing that the field dependence of energy barriers can be also extracted from relaxation measurements.

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The low field susceptibility of a textured superparamagnetic system

Cited by 55 publications

References 7 publications

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

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

Texture-induced magnetic interactions in ferrofluids

Magnetic field scaling of relaxation curves in small particle systems

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