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We consider a small itinerant ferromagnet exposed to an external magnetic field and strongly driven by a thermally induced spin current. For this model, we derive the quasi-classical equations of motion for the magnetization where the…

Mesoscale and Nanoscale Physics · Physics 2019-01-30 Tim Ludwig , Igor S. Burmistrov , Yuval Gefen , Alexander Shnirman

Starting from the Dirac-Kohn-Sham equation we derive the relativistic equation of motion of spin angular momentum in a magnetic solid under an external electromagnetic field. This equation of motion can be written in the form of the…

Materials Science · Physics 2016-10-20 Ritwik Mondal , Marco Berritta , Peter M. Oppeneer

It is well known that the Gilbert relaxation time of a magnetic moment scales inversely with the magnitude of the externally applied field, H, and the Gilbert damping, {\alpha}. Therefore, in ultrashort optical pulses, where H can…

Optics · Physics 2024-01-04 Benjamin Assouline , Amir Capua

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

The Landau--Lifshitz equation describes the dynamics of magnetization inside a ferromagnet. This equation is nonlinear and has an infinite number of stable equilibria. It is desirable to control the system from one equilibrium to another. A…

Optimization and Control · Mathematics 2015-09-29 Amenda Chow , Kirsten A. Morris

This paper describes a robust, modular, and physics- based circuit framework to model conventional and emerging Magnetic Tunnel Junction (MTJ) devices. Magnetization dynamics are described by the stochastic Landau-Lifshitz-Gilbert (sLLG)…

Mesoscale and Nanoscale Physics · Physics 2018-08-23 Mustafa Mert Torunbalci , Pramey Upadhyaya , Sunil A. Bhave , Kerem Y. Camsari

A theoretical model based on the Landau-Lifshitz-Bloch equation is developed to study the spin-torque effect in ferrimagnets. Experimental findings, such as the temperature dependence, the peak in spin torque, and the angular-momentum…

Materials Science · Physics 2018-11-21 Zhifeng Zhu , Xuanyao Fong , Gengchiau Liang

Using an effective Hamiltonian including the Zeeman and internal interactions, we describe the quantum theory of magnetization dynamics when the spin system evolves non-adiabatically and out of equilibrium. The Lewis-Riesenfeld dynamical…

Other Condensed Matter · Physics 2008-11-26 F. M. Saradzhev , F. C. Khanna , Sang Pyo Kim , M. de Montigny

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

Spin torque oscillators are conventionally described by the Landau-Lifshitz-Gilbert-Slonczewski (LLGS) equation. However, at the onset of oscillations, the predictions of the conventional LLGS equation differ qualitatively from experimental…

Mesoscale and Nanoscale Physics · Physics 2024-01-17 Pieter M. Gunnink , Tim Ludwig , Rembert A. Duine

We present efficient numerical methods for the simulation of small magnetization oscillations in three-dimensional micromagnetic systems. Magnetization dynamics is described by the Landau-Lifshitz-Gilbert (LLG) equation, linearized in the…

Computational Physics · Physics 2023-01-18 Massimiliano d'Aquino , Riccardo Hertel

The stochastic Landau--Lifshitz--Gilbert (LLG) equation describes the behaviour of the magnetization under the influence of the effective field consisting of random fluctuations. We first reformulate the equation into an equation the…

Numerical Analysis · Mathematics 2015-02-05 Beniamin Goldys , Kim-Ngan Le , Thanh Tran

We propose a theoretical model of magnetization switching in a ferromagnetic multilayer by both electric current and microwaves. The electric current gives a spin transfer torque on the magnetization, while the microwaves induce a…

Mesoscale and Nanoscale Physics · Physics 2016-01-22 Tomohiro Taniguchi , Daisuke Saida , Yoshinobu Nakatani , Hitoshi Kubota

We consider an electron interacting locally with two-level systems (TLSs) as an archetypal model for charge transport in the presence of inelastic scatterers. To assess the importance of quantum effects in the optical and d.c. conductivity…

Strongly Correlated Electrons · Physics 2025-09-25 Hadi Rammal , Sergio Ciuchi , Simone Fratini

A phase diagram of the magnetization dynamics is studied by numerically solving the Landau-Lifshitz-Gilbert (LLG) equation in a spin torque oscillator consisting of asymmetric two free layers that are magnetized in in-plane direction. We…

Mesoscale and Nanoscale Physics · Physics 2019-04-19 Tomohiro Taniguchi

We study dynamics of the magnetization coupled to the surface Dirac fermions of a three di- mensional topological insulator. By solving the Landau-Lifshitz-Gilbert equation in the presence of charge current, we find current induced…

Mesoscale and Nanoscale Physics · Physics 2015-05-28 Takehito Yokoyama

Understanding the magnetization switching process in ferromagnetic thin films is essential for many technological applications. We investigate the effects of periodic driving via magnetic fields on a macrospin system under explicit…

Materials Science · Physics 2022-08-16 Michael Maihöfer , Johannes Reiff , Jörg Main , Rigoberto Hernandez

By using the quantum kinetic approach with the instantaneous local equilibrium approximation, we propose an equation that is capable of addressing magnetization dynamics for a wide range of temperatures. The equation reduces to the…

Mesoscale and Nanoscale Physics · Physics 2015-06-05 Lei Xu , Shufeng Zhang

We consider the general Landau-Lifshitz-Gilbert theory underlying the magnetization dynamics of a macrospin magnet subject to spin-torque effects and thermal fluctuations. Thermally activated dynamical properties are analyzed by averaging…

Mesoscale and Nanoscale Physics · Physics 2013-10-07 Daniele Pinna , Andrew D. Kent , Daniel L. Stein

The Landau-Lifshitz-Gilbert equation for rigid and saturated ferromagnets is derived using a two-continuum model constructed by H.F. Tiersten for elastic and saturated ferromagnets. The relevant basic laws of physics are applied…

Materials Science · Physics 2023-05-30 Jiashi Yang