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We study the magnetization dynamics in a nanocontact magnetic vortex oscillators as function of temperature. Low temperature experiments reveal that the dynamics at low and high currents differ qualitatively. At low currents, we excite a…

We provide experimental and numerical evidence for thermal excitations within and among magnetic mesospins, forming artificial spin ice structures. At low temperatures, a decrease in magnetization and increase in susceptibility is observed…

Mesoscale and Nanoscale Physics · Physics 2023-02-14 Björn Erik Skovdal , Samuel D. Slöetjes , Merlin Pohlit , Henry Stopfel , Vassilios Kapaklis , Björgvin Hjörvarsson

We follow the dynamics of an ensemble of interacting self-propelled semi-flexible polymers in contact with a thermal bath. We characterize structure and dynamics of the passive system and as a function of the motor activity. We find that…

Soft Condensed Matter · Physics 2014-04-14 Davide Loi , Stefano Mossa , Leticia F. Cugliandolo

The lattice spin model, with nearest neighbor ferromagnetic exchange and long range dipolar interaction, is studied by the method of time series for observables based on cluster configurations and associated partitions, such as Shannon…

Disordered Systems and Neural Networks · Physics 2009-11-10 M. Casartelli , L. Dall'Asta , E. Rastelli , S. Regina

Using micromagnetic simulations, we have investigated spin dynamics in a nanostructure in the presence of thermal fluctuations. In particular, we have studied the effects of a uniform temperature and of a uniform thermal gradient. In both…

Mesoscale and Nanoscale Physics · Physics 2013-03-13 Simone Borlenghi , Matteo Franchin , Hans Fangohr , Lars Bergqvist , Anna Delin

The present work is devoted to the derivation of an effective magnon-paramagnon theory starting from a microscopic lattice model of ferromagnetic metals. For some values of the microscopic parameters it reproduces the Heisenberg theory of…

Condensed Matter · Physics 2009-10-31 N. I. Karchev

Based on classical statistical thermodynamics, we develop a theoretical approach that provides new insight into how macroscopic and microscopic physical properties are bridged via crystal lattice for condensed mat- ters. We find that in…

Materials Science · Physics 2016-05-18 Koretaka Yuge

In this work, we study the effect of dipole-dipole interparticle interactions on the static thermodynamic and magnetic properties of an ensemble of immobilized monodisperse superparamagnetic nanoparticles. We assume that magnetic…

Materials Science · Physics 2020-11-17 Anna Yu. Solovyova , Sergey A. Sokolsky , Ekaterina A. Elfimova , Alexey O. Ivanov

A new finite-size scaling approach based on the transfer matrix method is developed to calculate the critical temperature of anisotropic two-layer Ising ferromagnet, on strips of r wide sites of square lattices. The reduced internal energy…

Statistical Mechanics · Physics 2007-05-23 M. Ghaemi , M. Ghannadi , B. Mirza

The demagnetizing factor N is of both conceptual interest and practical importance. Considering localized magnetic moments on a lattice, we show that for non-ellipsoidal samples, N depends on the spin dimensionality (Ising, XY, or…

Ground-state properties of a two-dimensional system of superconducting vortices in the presence of a periodic array of strong pinning centers are studied analytically and numerically. The ground states of the vortex system at different…

Superconductivity · Physics 2009-11-07 Toby Joseph , Chandan Dasgupta

Magnetricity- the magnetic equivalent of electricity- was recently verified experimentally for the first time. Indeed, just as the stream of electric charges produces electric current, emergent magnetic monopoles have been observed to roam…

Mesoscale and Nanoscale Physics · Physics 2014-04-17 R. P. Loreto , L. A. Morais , R. C. Silva , F. S. Nascimento , C. I. L. de Araujo , L. A. S. Mól , W. A. Moura-Melo , A. R. Pereira

We investigate various possible definitions of an effective temperature for a particularly simple nonequilibrium stationary system, namely a heated Brownian particle suspended in a fluid. The effective temperature based on the fluctuation…

Statistical Mechanics · Physics 2011-05-30 Laurent Joly , Samy Merabia , Jean-Louis Barrat

We propose a systematic way to investigate the low-temperature thermodynamic properties of quantum spin systems subject to the restriction that only a finite number of bosons may occupy a single lattice site. Such a kinematical interaction…

Soft Condensed Matter · Physics 2016-08-31 L. V. Popovich , M. V. Medvedev

A detailed study of the analytic structure of 1-loop self energy graphs for neutral and charged $\rho$ mesons is presented at finite temperature and arbitrary magnetic field using the real time formalism of thermal field theory. The…

High Energy Physics - Phenomenology · Physics 2018-01-03 Snigdha Ghosh , Arghya Mukherjee , Mahatsab Mandal , Sourav Sarkar , Pradip Roy

Spin transfer torque from spin-polarized electrical current can excite large-amplitude magnetization dynamics in metallic ferromagnets of nanoscale dimensions. Since magnetic anisotropy energies of nanomagnets are comparable to the thermal…

Mesoscale and Nanoscale Physics · Physics 2010-07-23 Xiao Cheng , Carl T. Boone , Jian Zhu , I. N. Krivorotov

The temperature dependence of the anomalous sector of the effective action of fermions coupled to external gauge and pseudo-scalar fields is computed at leading order in an expansion in the number of Lorentz indices in two and four…

High Energy Physics - Theory · Physics 2016-08-25 L. L. Salcedo

The interplay between topology and energy-hierarchy plays a vital role in the collective magnetic order in artificial ferroic systems. Here we investigate, experimentally, the effect of having one or two activation energies of interacting…

Mesoscale and Nanoscale Physics · Physics 2021-12-02 Henry Stopfel , Unnar B. Arnalds , Aaron Stein , Thomas P. A. Hase , Björgvin Hjörvarsson , Vassilios Kapaklis

We have performed realistic atomistic simulations at finite temperatures using Monte Carlo and atomistic spin dynamics simulations incorporating quantum (Bose-Einstein) statistics. The description is much improved at low temperatures…

Materials Science · Physics 2018-01-10 Lars Bergqvist , Anders Bergman

Applied magnetic fields are an important tuning parameter for artificial spin ice (ASI) systems, as they can drive phase transitions between different magnetic ground states, or tune through regimes with high populations of emergent…

Mesoscale and Nanoscale Physics · Physics 2022-03-14 M. Goryca , X. Zhang , J. D. Watts , C. Nisoli , C. Leighton , P. Schiffer , S. A. Crooker