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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

Temperature-dependent magnetic properties of Nd$_2$Fe$_{14}$B permanent magnets, i.e., saturation magnetization $M_\text{s}(T)$, effective magnetic anisotropy constants $K_i^\text{eff}(T)$ ($i=1,2,3$), domain wall width $\delta_w(T)$, and…

Materials Science · Physics 2019-06-18 Qihua Gong , Min Yi , Richard F. L. Evans , Bai-Xiang Xu , Oliver Gutfleisch

We study theoretically the influence of the temperature and disorder on the spin wave spectrum of the magnonic crystal Fe$_{1-c}$Co$_{c}$. Our formalism is based on the analysis of a Heisenberg Hamiltonian by means of the wave vector and…

Materials Science · Physics 2023-01-06 Sebastian Paischer , Paweł A. Buczek , Nadine Buczek , David Eilmsteiner , Arthur Ernst

In this paper I give a detailed account of an ab initio methodology for describing strong electronic correlations in nanoscale devices hosting transition metal atoms with open $d$- or $f$-shells. The method combines Kohn-Sham Density…

Mesoscale and Nanoscale Physics · Physics 2015-06-15 D. Jacob

Temperature-dependent magnetic experiments like pump-probe measurements generated by a pulsed laser have become a crucial technique for switching the magnetization in the picosecond time scale. Apart from having practical implications on…

We investigate the emergence of ferromagnetism in the two-dimensional metal-halide CoBr$_2$, with a special focus on the role of electronic correlations. The calculated phonon spectrum shows that the system is thermodynamically stable…

Strongly Correlated Electrons · Physics 2021-05-13 Hrishit Banerjee , Markus Aichhorn

An accurate prediction of atomic diffusion in Fe alloys is challenging due to thermal magnetic excitations and magnetic transitions. We propose an effcient approach to address these properties via Monte Carlo simulation, using ab-initio…

Materials Science · Physics 2020-08-06 Anton Schneider , Chu Chun Fu , Frederic Soisson , Cyrille Barreteau

The electronic structure and magnetic exchange interactions in pure and V-doped Fe16N2 are studied within the framework of density functional theory. The Curie temperatures were obtained with both mean field approximation (MFA) as well as…

Materials Science · Physics 2018-10-24 Satadeep Bhattacharjee , Seung-Cheol Lee

We consider electronic correlation effects and their impact on magnetic properties of tetragonally distorted chemically ordered FeCo alloys (L1$_0$ structure) being a promising candidate for rare-earth-free permanent magnets. We employ a…

Strongly Correlated Electrons · Physics 2022-06-02 A. S. Belozerov , A. A. Katanin , V. I. Anisimov

We investigate the contributions of finite-temperature magnetic fluctuations to the thermodynamic properties of bcc Fe as a function of pressure. First, we apply a tight-binding total-energy model parameterized to first-principles…

Materials Science · Physics 2010-07-21 Xianwei Sha* , R. E. Cohen

We propose a new ab initio method designed for the accurate calculation of effective exchange integrals between atoms with numerous open-shells. This method applies to ferromagnetic as well as antiferromagnetic exchange, direct or…

Strongly Correlated Electrons · Physics 2015-05-13 Alain Gellé , Julien Varignon , Marie-Bernadette Lepetit

Detailed experimental investigations of thermal and magnetic properties are presented for Cu(NH3)4SO4.H2O, an ideal uniform Heisenberg spin half chain compound. A comparison of these properties with relevant spin models is also presented.…

Strongly Correlated Electrons · Physics 2019-01-01 Tanmoy Chakraborty , Harkirat Singh , Dipanjan Chaudhuri , Hirale S. Jeevan , Philipp Gegenwart , Chiranjib Mitra

We employ state-of-the-art ab initio simulations within the dynamical mean-field theory to study three likely phases of iron (hexogonal close-packed, hcp, face centered cubic, fcc, and body centered cubic, bcc) at the Earth's core…

Strongly Correlated Electrons · Physics 2013-03-25 L. V. Pourovskii , T. Miyake , S. I. Simak , A. V. Ruban , L. Dubrovinsky , I. A. Abrikosov

We theoretically study the magnetic properties of iron germanium, known as one of canonical helimagnets. For this purpose we use the real-space spin Hamiltonian and micromagnetic model, derived in terms of Andersen's "local force theorem",…

Strongly Correlated Electrons · Physics 2018-03-28 Ilya V. Kashin , Sergey N. Andreev , Vladimir V. Mazurenko

Quantum simulation of the XXZ model with a two-component Bose or Fermi Hubbard model based on a Mott insulator background has been widely used in the investigations of quantum magnetism with ultracold neutral atoms. In most cases, the…

Achieving long-range ferrimagnetic order in purely organic systems remains a major challenge in molecular magnetism. Here we report the synthesis and characterization of heterospin-coupling motifs, formed by covalently linking spin-1/2 and…

Mesoscale and Nanoscale Physics · Physics 2026-04-10 Elia Turco , Fupeng Wu , Annika Bernhardt , Nils Krane , Ji Ma , Roman Fasel , Michal Juriček , Xinliang Feng , Pascal Ruffieux

Magnetoelasticity plays a crucial role in numerous magnetic phenomena, including magnetocalorics, magnon excitation via acoustic waves, and ultrafast demagnetization/Einstein-de Haas effect. Despite a long-standing discussion on…

After the discovery of the phenomena of light-induced excited spin state trapping (LIESST), the functional properties of metal complexes have been studied intensively. Among them, cooperative phenomena involving low spin-high spin…

Materials Science · Physics 2009-11-11 Kamel Boukheddaden , Masamichi Nishino , Seiji Miyashita , Francois Varret

We study the critical behavior of a quenched random-exchange Ising model with competing interactions on a bcc lattice. This model was introduced in the study of the magnetic behavior of Fe_{1-x}Ru_x alloys for ruthenium concentrations x=0%,…

Statistical Mechanics · Physics 2017-10-31 I. J. L. Diaz , N. S. Branco

We use an exact numerical diagonalization method to calculate the dynamical spin structure factors (DSFs) of three ab-initio models and one ab-initio-guided model for a honeycomb-lattice magnet $\alpha$-RuCl$_3$. We also use thermal pure…

Strongly Correlated Electrons · Physics 2019-06-07 Takafumi Suzuki , Sei-ichiro Suga