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A temperature dependent coherent magnetization reversal model is proposed for size-distributed assemblies of ferromagnetic nanoparticles and ferromagnetic-antiferromagnetic core-shell nanoparticles. The nanoparticles are assumed to be of…

Using the two-level approximation of the energy barrier, we perform extensive kinetic Monte Carlo simulations to probe the relaxation characteristics in a two-dimensional ($L^{}_x\times L^{}_y$) array of magnetic nanoparticle as a function…

Materials Science · Physics 2022-03-23 Manish Anand

In application as hyperthermia and nanowarming, power dissipation arises when the time-dependent magnetization $M(t)$ of an out-of-equilibrium system of nanoparticles lags behind the applied field $H(t)$. The key parameter governing this…

Mesoscale and Nanoscale Physics · Physics 2024-06-07 Pedro Mendoza Zélis , Daniel G. Actis , Giuliano A. Basso , Gustavo A. Pasquevich , Ignacio J. Bruvera

The interaction of coherent magnetization rotation with a system of two-level impurities is studied. Two different, but not contradictory mechanisms, the `slow-relaxing ion' and the `fast-relaxing ion' are utilized to derive a system of…

Condensed Matter · Physics 2009-10-31 Vladimir L. Safonov , H. Neal Bertram

The magnetization reversal time of ferromagnetic nanoparticles is investigated in the very low damping regime. The energy-controlled diffusion equation rooted in a generalization of the Kramers escape rate theory for point Brownian…

Statistical Mechanics · Physics 2014-04-07 William T. Coffey , Yuri P. Kalmykov , Serguey V. Titov

We discuss numerical and theoretical results for models of magnetization switching in nanoparticles and ultrathin films. The models and computational methods include kinetic Ising and classical Heisenberg models of highly anisotropic…

Materials Science · Physics 2007-05-23 Per Arne Rikvold , Gregory Brown , Steven J. Mitchell , M. A. Novotny

Magnetization reversal of individual, isolated high-aspect-ratio Fe nanoparticles with diameters comparable to the magnetic exchange length is studied by high-sensitivity submicron Hall magnetometry. For a Fe nanoparticle with diameter of 5…

Materials Science · Physics 2009-11-11 Yongqing Li , Peng Xiong , Stephan von Molnar , Yuzo Ohno , Hideo Ohno

The switching dynamics of a single-domain BiFeO$_3$ thin films is investigated through combining the dynamics of polarization and Neel vector. The evolution of the ferroelectric polarization is described by the Landau-Khalatnikov (LK)…

Mesoscale and Nanoscale Physics · Physics 2021-02-03 Yu-Ching Liao , Dmitri E. Nikonov , Sourav Dutta , Sou-Chi Chang , Sasikanth Manipatruni , Ian A. Young , Azad Naeemi

It has been shown that a single-domain magnetic nanoparticle can be effectively switched by a linear down-chirp microwave field pulse (DCMWP) in zero temperature limit. However, finite temperature is ubiquitous in practice. Here, we study…

Mesoscale and Nanoscale Physics · Physics 2021-06-21 M. T. Islam , M. A. J. Pikul , X. S. Wang

We report numerical and analytical studies of the reversal of the magnetic moment of a single-domain magnetic particle by a circularly polarized ac field of time-dependent frequency. For the time-linear frequency sweep, the phase diagrams…

Mesoscale and Nanoscale Physics · Physics 2014-01-07 Liufei Cai , D. A. Garanin , E. M. Chudnovsky

We present a general study of frequency and magnetic field dependence of the specific heat power produced during field-driven hysteresis cycles in magnetic nanoparticles with relevance to hyperthermia applications in biomedicine. Employing…

Materials Science · Physics 2014-12-15 S. Ruta , O. Hovorka , R. Chantrell

Spin relaxation in the ultrathin metallic films of stacked microelectronic devices is investigated on the basis of a modified Landau-Lifshitz equation of micromagnetic dynamics in which the damping torque is treated as originating from the…

Materials Science · Physics 2012-10-22 Sergey Bastrukov , Jun Yong Khoo , Boris Lukiyanchuk , Irina Molodtsova

Thermal fluctuations of nanomagnets driven by spin-polarized currents are treated via the Landau-Lifshitz-Gilbert equation generalized to include both the random thermal noise field and the Slonczewski spin-transfer torque term. By…

Statistical Mechanics · Physics 2013-10-09 Y. P. Kalmykov , W. T. Coffey , S. V. Titov , J. E. Wegrowe , D. Byrne

The energy loss of a relativistic charge undergoing multiple scatterings while traversing an infinite, polarizable and absorptive plasma is investigated. Polarization and damping mechanisms in the medium are phenomenologically modelled by a…

High Energy Physics - Phenomenology · Physics 2012-09-18 Marcus Bluhm , Pol Bernard Gossiaux , Joerg Aichelin

Magnetization reversal in permanent magnets occurs by the nucleation and expansion of reversed domains. Micromagnetic theory offers the possibility to localize the spots within the complex structure of the magnet where magnetization…

Materials Science · Physics 2018-05-25 J. Fischbacher , A. Kovacs , L. Exl J. Kühnel , E. Mehofer , H. Sepehri-Amin , T. Ohkubo , K. Hono , T. Schrefl

By applying a variational principle on a magnetic system within the framework of extended irreversible thermodynamics, we find that the presence of a temperature gradient in a ferromagnet leads to a generalisation of the Landau-Lifshitz…

Materials Science · Physics 2015-10-12 Sylvain D. Brechet , Jean-Philippe Ansermet

We consider the general Landau-Lifshitz-Gilbert (LLG) dynamical theory underlying the magnetization switching rates of a thin film uniaxial magnet subject to spin-torque effects and thermal fluctuations (thermal noise). After discussing the…

Mesoscale and Nanoscale Physics · Physics 2013-08-01 D. Pinna , A. D. Kent , D. L. Stein

We study the effect of a magnetic field on the thermal relaxation of non-interacting small monodomain particle systems particles with a distribution of anisotropy constants and random easy-axes directions. Numerical calculations of the…

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

The shape of ferromagnetic resonance spectra of highly dispersed, chemically disordered Fe_{0.2}Pt_{0.8} nanospheres is perfectly described by the solution of the Landau-Lifshitz-Gilbert (LLG) equation excluding effects by crystalline…

Other Condensed Matter · Physics 2009-11-13 Jürgen Kötzler , Detlef Görlitz , Frank Wiekhorst

We consider a dilute ensemble of randomly-oriented noninteracting spherical nanomagnets and investigate its magnetization structure and ensuing neutron-scattering response by numerically solving the Landau-Lifshitz equation. Taking into…

Mesoscale and Nanoscale Physics · Physics 2022-05-17 Michael P. Adams , Andreas Michels , Hamid Kachkachi