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Magnetic nanoparticles with Neel surface anisotropy, different internal structures, surface arrangements and elongation are modelled as many-spin systems. The results suggest that the energy of many-spin nanoparticles cut from cubic…

Statistical Mechanics · Physics 2008-05-06 R. Yanes , O. Chubykalo-Fesenko , H. Kachkachi , D. A. Garanin , R. Evans , R. W. Chantrell

We calculate the contribution of the Neel surface anisotropy to the effective anisotropy of magnetic nanoparticles of spherical shape cut out of a simple cubic lattice. The effective anisotropy arises because deviations of atomic…

Statistical Mechanics · Physics 2009-11-07 D. A. Garanin , H. Kachkachi

We investigate the effect of surface anisotropy in a spherical many-spin magnetic nanoparticle. By computing minor loops, two-dimensional (2D) and 3D energyscape, and by investigating the behavior of the net magnetization, we show that in…

Statistical Mechanics · Physics 2009-11-11 H. Kachkachi , E. Bonet

We investigate the signature of magnetic surface anisotropy in nanoparticles in their spin-flip neutron scattering cross section. Taking into account the isotropic exchange interaction, an external magnetic field, a uniaxial or cubic…

Materials Science · Physics 2023-11-13 Michael P. Adams , Evelyn Pratami Sinaga , Hamid Kachkachi , Andreas Michels

We present a review of recent advances in the study of many-body effects in magnetic nanoparticles. Considering classical spins on a lattice coupled by the exchange interaction in the presence of the bulk and surface anisotropy, we…

Statistical Mechanics · Physics 2016-08-31 H. Kachkachi , D. A. Garanin

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 $T\ln(t/\tau_0)$ scaling approach. The comparison between the distributions of the…

An attractive feature of magnetic adatoms and molecules for nanoscale applications is their superparamagnetism, the preferred alignment of their spin along an easy axis preventing undesired spin reversal. The underlying magnetic anisotropy…

Mesoscale and Nanoscale Physics · Physics 2014-07-22 Maciej Misiorny , Michael Hell , Maarten R. Wegewijs

The influence of surface anisotropy on the magnetization processes of maghemite nanoparticles with ellipsoidal shape is studied by means of Monte Carlo simulations. Radial surface anisotropy is found to favor the formation of hedgehog-like…

Materials Science · Physics 2007-05-23 Oscar Iglesias , Amilcar Labarta

The specific absorption rate (SAR) of a dilute assembly of spherical iron nanoparticles with cubic anisotropy distributed in a viscous liquid is calculated using the solution of stochastic Landau - Lifshitz equation for unit magnetization…

Mesoscale and Nanoscale Physics · Physics 2021-10-04 E. M. Gubanova , R. A. Rytov , N. A. Usov

We study the finite-size and surface effects on the thermal and spatial behaviors of the magnetisation of a small magnetic particle. We consider two systems: 1) A box-shaped isotropic particle of simple cubic structure with either periodic…

Materials Science · Physics 2009-10-31 H. Kachkachi , M. Nogues , E. Tronc , D. A. Garanin

We calculate the magnetic SANS cross section of dilute ensembles of uniformly magnetized and randomly-oriented Stoner-Wohlfarth particles using the Landau-Lifshitz equation. The focus of our study is on the angular anisotropy of the…

Materials Science · Physics 2022-10-18 Michael P. Adams , Evelyn Pratami-Sinaga , Andreas Michels

Permanent magnet materials require a high uniaxial magneto-crystalline anisotropy. Exchange coupling between small crystallites with easy-plane anisotropy induces an effective uniaxial anisotropy if arranged accordingly. Nanostructuring of…

Materials Science · Physics 2017-11-10 J. Fischbacher , A. Kovacs , H. Oezelt , M. Gusenbauer , D. Suess , T. Schrefl

We study the influence of surface anisotropy on the zero-temperature hysteretic properties of a small single-domain magnetic particle, and give an estimation of the anisotropy constant for which deviations from the Stoner-Wohlfarth model…

Statistical Mechanics · Physics 2009-11-07 H. Kachkachi , M. Dimian

High fraction of the surface atoms considerably enhances the influence of size and shape on the magnetic and electronic properties of nanoparticles. Shape effects in ferromagnetic nanoparticles are well understood and allow to set and…

Mesoscale and Nanoscale Physics · Physics 2013-08-16 H. Gomonay , S. Kondovych , V. Loktev

We consider a single spherical nanomagnet and investigate the spatial magnetization profile $\mathbf{m}\left(\mathbf{r}\right)$ in the continuum approach, using the Green's function formalism. The energy of the (many-spin) nanomagnet…

Mesoscale and Nanoscale Physics · Physics 2023-09-13 M. P. Adams , A. Michels , H. Kachkachi

We study the influence of surface anisotropy on the zero-temperature hysteretic properties of a small single-domain magnetic particle, and give an estimation of the anisotropy constant for which deviations from the Stoner-Wohlfarth model…

Statistical Mechanics · Physics 2009-11-07 M. Dimian , H. Kachkachi

We present a general approach to the derivation of the effective anisotropy field which determines the dynamical behaviour of magnetic spins according to the Landau-Lifshitz-Gilbert equation. The approach is based on the gradient in…

The temperature dependence of magnetic anisotropy in (113)A (Ga,Mn)As layers grown by molecular beam epitaxy is studied by means of superconducting quantum interference device (SQUID) magnetometry as well as by ferromagnetic resonance (FMR)…

We study the effect of surface anisotropy on the spectrum of spin-wave excitations in a magnetic nanocluster and compute the corresponding absorbed power. For this, we develop a general numerical method based on the (undamped)…

Mesoscale and Nanoscale Physics · Physics 2016-12-21 R. Bastardis , F. Vernay , D. -A. Garanin , H. Kachkachi

We study the effective anisotropy induced in thin nanomagnets by the nonlocal demagnetization field (dipole-dipole interaction). Assuming a magnetization independent of the thickness coordinate, we reduce the energy to an inhomogeneneous…

Strongly Correlated Electrons · Physics 2008-01-29 Jean-Guy Caputo , Yuri Gaididei , Volodymyr P. Kravchuk , Franz G. Mertens , Denis D. Sheka
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