Surface-induced anisotropy and multiple states in elongated magnetic nanoparticles

Leonov, A. A.; Dragunov, I. E.; Bogdanov, A. N.

doi:10.1063/1.2737830

Cited by 5 publications

(10 citation statements)

References 16 publications

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“…Many of the results of these calculations reproduce most of the anomalous properties associated with surface-anisotropy effects observed in fine particle systems. In particular, a simple phenomenological model based on this assumption [18] has been used to calculate the astroids corresponding to the phase diagrams for ellipsoidal particles which are in agreement with recent micro-SQUID experiments on isolated particles [19].…”

Section: Introductionsupporting

confidence: 68%

“…The ad hoc assumption of a surface anisotropy normal to the particle surface and described by a uniform surface density K s has also been applied to the study of the magnetization and switching processes of a single particle in many numerical calculations based on atomistic Monte Carlo simulations [13,14,15,16], Landau-Lifshitz-Gilbert equation [13,17] and micromagnetics models [18]. Many of the results of these calculations reproduce most of the anomalous properties associated with surface-anisotropy effects observed in fine particle systems.…”

Section: Introductionmentioning

confidence: 99%

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Surface anisotropy broadening of the energy barrier distribution in magnetic nanoparticles

et al. 2008

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The effect of surface anisotropy on the distribution of energy barriers in magnetic fine particles of nanometer size is discussed within the framework of the Tln(t/τ(0)) scaling approach. The comparison between the distributions of the anisotropy energy of the particle cores, calculated by multiplying the volume distribution by the core anisotropy, and of the total anisotropy energy, deduced by deriving the master curve of the magnetic relaxation with respect to the scaling variable Tln(t/τ(0)), enables the determination of the surface anisotropy as a function of the particle size. We show that the contribution of the particle surface to the total anisotropy energy can be well described by a size-independent value of the surface energy per unit area which permits the superimposition of the distributions corresponding to the particle core and effective anisotropy energies. The method is applied to a ferrofluid composed of non-interacting Fe(3-x)O(4) particles of 4.9 nm average size and x about 0.07. Even though the size distribution is quite narrow in this system, a relatively small value of the effective surface anisotropy constant K(s) = 2.9 × 10(-2) erg cm(-2) gives rise to a dramatic broadening of the total energy distribution. The reliability of the average value of the effective anisotropy constant, deduced from magnetic relaxation data, is verified by comparing it to that obtained from the analysis of the shift of the ac susceptibility peaks as a function of the frequency.

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Section: Introductionsupporting

confidence: 68%

Section: Introductionmentioning

confidence: 99%

Surface anisotropy broadening of the energy barrier distribution in magnetic nanoparticles

et al. 2008

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“…The angle between the magnetization and the axis [110] is determined by the Eq. (15). For T=15K (the ratio κ = 0.42 was obtained from fits of the hard-axis magnetization curves and cal-culating the easy-axis orientation from Eq.…”

Section: Comparison With Experimentsmentioning

confidence: 99%

“…In magnetic nanostructures complex physical processes on surfaces and interfaces give rise to enhanced uniaxial magnetic anisotropies [1,2,3,4]. The interplay between these induced and intrinsic (magnetocrystalline) anisotropies strongly influences the magnetization processes in many important classes of nanoscaled systems, such as ferromagnet-antiferromagnet bilayers [5,6,7,8], thin epilayers of diluted magnetic semiconductors [9,10,11,12,13,14] or in magnetic nanoparticles [15,16,17,18,19], and is the reason of various remarkable effects involving complex spin reorientation [10,14,20,21,22,23,24,25,26,27,28] and the evolution of specific multidomain states [29,30,31,32,33].…”

Section: Introductionmentioning

confidence: 99%

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Phenomenological theory of magnetization reversal in nanosystems with competing anisotropies

Leonov

Rößler

Bogdanov

2008

Journal of Applied Physics

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The interplay between intrinsic and surface/interface-induced magnetic anisotropies strongly influences magnetization processes in nanomagnetic systems. We develop a micromagnetic theory to describe the field-driven reorientation in nanomagnets with cubic and uniaxial anisotropies. Spin configurations in competing phases and parameters of accompanying multidomain states are calculated as functions of the applied field and the magnetic anisotropies. The constructed magnetic phase diagrams allow to classify different types of the magnetization reversal and to provide detailed analysis of the switching processes in magnetic nanostructures. The calculated magnetization profiles of isolated domain walls show that the equilibrium parameters of such walls are extremely sensitive to applied magnetic field and values of the competing anisotropies and can vary in a broad range. For nanolayers with perpendicular anisotropy the geometrical parameters of stripe domains have been calculated as functions of a bias field. The results are applied to analyse the magnetization processes as observed in various nanosystems with competing anisotropies, mainly, in diluted magnetic semiconductor films (Ga,Mn)As. 75.50.Ee,

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Surface anisotropy in a magnetic cylinder induced by the displacement of a vortex core

Riveros

Carvajal

Escrig

2019

Journal of Magnetism and Magnetic Materials

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In this article we investigate the induction of a surface anisotropy due to the displacement of the vortex core in a cylindrical nanostructure. In fact, the effect of the displacement of the vortex core in the dipolar energy can be modeled simply as a surface anisotropy of the form Es = Ks Sm dS (n ·m) 2 /2. Moreover, the surface anisotropy constant Ks is proportional to the cylinder in-plane demagnetizing factor in the direction of the core deviation, Ny(L/R), i.e., Ks = µ0M 2 0 R Ny(L/R), where R and L are the radius and the thickness of the cylinder, respectively. Our results show that the term of the nontrivial dipolar energy caused by the charges in the cylinder mantle can be replaced by a simple integral Es that increases the efficiency of the numerical calculations in the analytical study of the displacement of the vortex core in magnetic vortices.

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Surface-induced anisotropy and multiple states in elongated magnetic nanoparticles

Abstract: Articles you may be interested inSpin wave mode transition induced by surface anisotropy and characteristic length in magnetic nanoparticles

Cited by 5 publications

References 16 publications

Surface anisotropy broadening of the energy barrier distribution in magnetic nanoparticles

Surface anisotropy broadening of the energy barrier distribution in magnetic nanoparticles

Phenomenological theory of magnetization reversal in nanosystems with competing anisotropies

Surface anisotropy in a magnetic cylinder induced by the displacement of a vortex core

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