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We present an ab initio theory of the Gilbert damping in substitutionally disordered ferromagnetic alloys. The theory rests on introduced nonlocal torques which replace traditional local torque operators in the well-known torque-correlation…

Materials Science · Physics 2015-12-09 Ilja Turek , Josef Kudrnovsky , Vaclav Drchal

The optimization of physical parameters serves various purposes, such as system identification and efficiency in developing devices. Spin-torque oscillators have been applied to neuromorphic computing experimentally and theoretically, but…

Mesoscale and Nanoscale Physics · Physics 2024-09-17 Yusuke Imai , Shuhong Liu , Nozomi Akashi , Kohei Nakajima

With appropriate modifications, the multi-spin Klein-Gordon (KG) equation of quantum field theory can be adapted to curved spacetime for spins 0,1,1/2. The associated particles in the microworld then move as a wave at all spacetime…

General Relativity and Quantum Cosmology · Physics 2021-11-24 Gary Nash

We present a phenomenological theory of spin-orbit torques in a metallic ferromagnet with spin-relaxing boundaries. The model is rooted in the coupled diffusion of charge and spin in the bulk of the ferromagnet, where we account for the…

Mesoscale and Nanoscale Physics · Physics 2021-07-14 Hector Ochoa , Ricardo Zarzuela , Yaroslav Tserkovnyak

Possible geometric frameworks for a unified theory of gravity and electromagnetism are investigated: General relativity is enlarged by allowing for an arbitrary complex linear connection and by constructing an extended spinor derivative…

High Energy Physics - Theory · Physics 2007-05-23 Kenichi Horie

An essential property of magnetic devices is the relaxation rate in magnetic switching which depends strongly on the damping in the magnetisation dynamics. It was recently measured that damping depends on the magnetic texture and,…

Materials Science · Physics 2018-01-10 Danny Thonig , Yaroslav Kvashnin , Olle Eriksson , Manuel Pereiro

In various background independent approaches, quantum gravity is defined in terms of a field propagation kernel: a sum over paths interpreted as a transition amplitude between 3-geometries, expected to project quantum states of the geometry…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Federico Mattei , Carlo Rovelli , Simone Speziale , Massimo Testa

We derive thermomagnonic torque and its "$\beta$-type" dissipative correction from the stochastic Landau-Lifshitz-Gilbert equation. The "$\beta$-type" dissipative correction describes viscous coupling between magnetic dynamics and magnonic…

Mesoscale and Nanoscale Physics · Physics 2015-05-27 Alexey A. Kovalev

An earlier scheme [arXiv:2404.03360], where torsion plays an essential part in a flat spacetime account of fermion spin, is extended to spacetimes with non-zero Riemann curvature. It is found that further essential features of the fermion,…

General Relativity and Quantum Cosmology · Physics 2024-04-18 William J. Leigh

The first computation of a spin foam dynamics that provides a test of the quantum equations of motions of gravity is presented. Specifically, a triangulation that includes an inner edge is treated. The computation leverages the recently…

General Relativity and Quantum Cosmology · Physics 2021-07-07 Seth K. Asante , Bianca Dittrich , Hal M. Haggard

The present thesis aims at an extension of the canonical formalism of Arnowitt, Deser, and Misner from self-gravitating point-masses to objects with spin. This would allow interesting applications, e.g., within the post-Newtonian (PN)…

General Relativity and Quantum Cosmology · Physics 2011-06-22 Jan Steinhoff

We extend the geometrical ideas of the spacetime deformations to study the physical foundation of the post-Riemannian geometry. To this aim, we construct the theory of 'two-step spacetime deformation' as a guiding principle. We address the…

General Relativity and Quantum Cosmology · Physics 2011-04-05 G Ter-Kazarian

A microscopic calculation is presented for the spin-transfer torques (STT) and damping torques in metallic antiferromagnets (AF). It is found that the sign of the STT is opposite to that in ferromagnets because of the AF transport…

Mesoscale and Nanoscale Physics · Physics 2021-05-26 Jotaro J. Nakane , Hiroshi Kohno

A characteristic feature of the Gaussian approximation in the functional-integral approach to the spin-fluctuation theory is the jump phase transition to the paramagnetic state. We eliminate the jump and obtain a continuous second-order…

Strongly Correlated Electrons · Physics 2010-04-27 N. B. Melnikov , B. I. Reser , V. I. Grebennikov

We derive a geometric representation of couplings between spin degrees of freedom and gauge fields within the worldline approach to quantum field theory. We combine the string-inspired methods of the worldline formalism with elements of the…

High Energy Physics - Theory · Physics 2009-11-11 Holger Gies , Jens Hammerling

Perturbative quantum gravity in the framework of the Schwinger-Keldysh formalism is applied to compute lowest-order corrections to the actual expansion of the Universe described in terms of the spatially flat…

High Energy Physics - Theory · Physics 2015-06-17 Bogusław Broda

We address the role of correlations between spin and charge degrees of freedom on the dynamical properties of ferromagnetic systems governed by the magnetic exchange interaction between itinerant and localized spins. For this we introduce a…

Strongly Correlated Electrons · Physics 2008-08-25 M. D. Kapetanakis , I. E. Perakis

In this work we take into consideration a generalization of Gauge Theories based on the analysis of the structural characteristics of Maxwell theory, which can be considered as the prototype of such kind of theories (Maxwell-like). Such…

General Relativity and Quantum Cosmology · Physics 2017-04-03 Germano Resconi , Ignazio Licata , Christian Corda

Relaxation effects are of primary importance in the description of magnetic excitations, leading to a myriad of methods addressing the phenomenological damping parameters. In this work, we consider several well-established forms of…

Mesoscale and Nanoscale Physics · Physics 2019-04-26 Filipe S. M. Guimarães , J. R. Suckert , Jonathan Chico , Juba Bouaziz , Manuel dos Santos Dias , Samir Lounis

We study the gravitational dynamics in the early inspiral phase of coalescing compact binaries using Non-Relativistic General Relativity (NRGR) - an effective field theory formalism based on the post-newtonian expansion, but which provides…

General Relativity and Quantum Cosmology · Physics 2016-11-15 Delphine L. Perrodin