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We simulate the spin torque-induced reversal of the magnetization in thin disks with perpendicular anisotropy at zero temperature. Disks typically smaller than 20 nm in diameter exhibit coherent reversal. A domain wall is involved in larger…

Mesoscale and Nanoscale Physics · Physics 2018-12-03 Paul Bouquin , Siddharth Rao , Gouri Sankar Kar , Thibaut Devolder

These lecture notes introduce quantum spin systems and several computational methods for studying their ground-state and finite-temperature properties. Symmetry-breaking and critical phenomena are first discussed in the simpler setting of…

Strongly Correlated Electrons · Physics 2015-03-17 Anders W. Sandvik

In this article, a few problems related to multiscale modelling of magnetic materials at finite temperatures and possible ways of solving these problems are discussed. The discussion is mainly centred around two established multiscale…

Computational Physics · Physics 2017-02-20 Doghonay Arjmand , Mikhail Poluektov , Gunilla Kreiss

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

It is proposed that nuclear (or electron) spins in a trapped molecule would be well isolated from the environment and the state of each spin can be measured by means of mechanical detection of magnetic resonance. Therefore molecular traps…

Quantum Physics · Physics 2007-05-23 Haiqing Wei , Xin Xue

Quantum entanglement is one of the core features of quantum theory. While it is typically revealed by measurements along carefully chosen directions, here we review different methods based on so-called random or randomized measurements.…

Quantum Physics · Physics 2020-11-24 Lukas Knips

We study macroscopic quantum tunneling of the magnetic moment in a single-domain particle placed above the surface of a superconductor. Such a setup allows one to manipulate the height of the energy barrier, preserving the degeneracy of the…

Mesoscale and Nanoscale Physics · Physics 2009-10-31 Eugene M. Chudnovsky , Jonathan R. Friedman

The time-dependent transport through single-molecule magnets coupled to magnetic or non-magnetic electrodes is studied in the framework of the generalized master equation method. We investigate the transient regime induced by the periodic…

Mesoscale and Nanoscale Physics · Physics 2015-09-02 V. Moldoveanu , I. V. Dinu , B. Tanatar , C. P. Moca

Nanomagnetism has recently attracted explosive attention, in particular, because of the enormous potential applications in information industry, e.g. new harddisk technology, race-track memory[1], and logic devices[2]. Recent technological…

Mesoscale and Nanoscale Physics · Physics 2015-05-18 Z. Z. Sun , Alexander Lopez , John Schliemann

Low-temperature magnetization curves of the classical frustrated ferromagnetic chain in the external magnetic field near the transition point between the ferromagnetic and the helical phases is studied. It is shown that the calculation of…

Statistical Mechanics · Physics 2013-05-29 D. V. Dmitriev , V. Ya. Krivnov , N. Yu. Kuzminyh

A new family of supramolecular, antiferromagnetically exchange-coupled dimers of single-molecule magnets (SMMs) has recently been reported [W. Wernsdorfer, N. Aliaga-Alcalde, D.N. Hendrickson, and G. Christou, Nature 416, 406 (2002)]. Each…

Mesoscale and Nanoscale Physics · Physics 2009-11-10 R. Tiron , W. Wernsdorfer , D. Foguet-Albiol , N. Aliaga-Alcalde , G. Christou

The nature of magnetization reversal in an isolated cylindrical nanomagnet has been studied employing time-resolved magnetoresistance measurement. We find that the reversal mode is highly stochastic, occurring either by multimode or…

Mesoscale and Nanoscale Physics · Physics 2015-05-20 Soumik Mukhopadhyay , Amrita Singh , Arindam Ghosh

The detailed theoretical understanding of quantum spin dynamics in various molecular magnets is an important step on the roadway to technological applications of these systems. Quantum effects in both ferromagnetic and antiferromagnetic…

Mesoscale and Nanoscale Physics · Physics 2007-05-23 Michael N. Leuenberger , Florian Meier , Daniel Loss

We identify the critical theory controlling the universal, low temperature, macroscopic properties of both quantum and classical ferromagnetic chains. The theory is the quantum mechanics of a single rotor. The mapping leads to an efficient…

Condensed Matter · Physics 2009-10-28 Minoru Takahashi , Hiroaki Nakamura , Subir Sachdev

Properties of nanoparticles have been studied within the framework of Ising model and the method of random-field interactions: the average magnetic moment and position of critical points of the magnetic and the concentration phase…

Mesoscale and Nanoscale Physics · Physics 2014-02-21 Yury Kirienko , Leonid Afremov

Spin reversal in magnetic nanomolecules and nanoclusters is considered. A method is suggested allowing, from one side, to keep for long time magnetic polarization in a metastable state and, from the other side, for starting the reversal…

Mesoscale and Nanoscale Physics · Physics 2022-03-23 V. I. Yukalov , E. P. Yukalova

A key to building functional devices on the basis of single molecule magnets in the framework of molecular electronics is the ability to deposit and study these molecules on a surface, because the structural, electronic and magnetic…

Mesoscale and Nanoscale Physics · Physics 2016-01-26 Judith Donner , Jan-Philipp Broschinski , Bastian Feldscher , Anja Stammler , Hartmut Bögge , Thorsten Glaser , Daniel Wegner

We apply a recently developed quantum theory of spin transfer torque to study the effect of the quantum noise in spin transfer process on the magnetization switching in spin-torque-driven devices. The quantum noise induces considerable…

Mesoscale and Nanoscale Physics · Physics 2013-07-10 Yong Wang , Yan Zhou , Fu-Chun Zhang

Measurements of magnetic hysteresis loops in single Co nanoparticles at dilution refrigerator temperatures are presented. The nanoparticles are in electric contact with bulk Al leads via tunnel junctions. The tunnel current versus magnetic…

Mesoscale and Nanoscale Physics · Physics 2012-07-10 F. Tijiwa Birk , W. Jiang , D. Davidović

Spin-polarized low-energy electron microscopy was used to image a magnetite crystal with (100) surface orientation. Sets of spin-dependent images of magnetic domain patterns observed in this surface were used to map the direction of the…

Materials Science · Physics 2013-11-11 Juan de la Figuera , Lucía Vergara , Alpha T. N'Diaye , Adrian Quesada , Andreas K. Schmid