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Entropy 2009, 11(4), 548-559; doi:10.3390/e11040548
Article

The Quantum Noise of Ferromagnetic π-Bloch Domain Walls

Department of Applied Maths, School of Mathematics, University of Leeds, Leeds, LS2 9JT, UK
Received: 27 August 2009 / Accepted: 23 September 2009 / Published: 28 September 2009
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Abstract

We quantify the probability per unit Euclidean-time of reversing the magnetization of a π-Bloch vector, which describes the Ferromagnetic Domain Walls of a Ferromagnetic Nanowire at finite-temperatures. Our approach, based on Langer’s Theory, treats the double sine-Gordon model that defines the π-Bloch vectors via a procedure of nonperturbative renormalization, and uses importance sampling methods to minimise the free energy of the system and identify the saddlepoint solution corresponding to the reversal probability. We identify that whilst the general solution for the free energy minima cannot be expressed in closed form, we can obtain a closed expression for the saddlepoint by maximizing the entanglement entropy of the system as a polynomial ring. We use this approach to quantify the geometric and non-geometric contributions to the entanglement entropy of the Ferromagnetic Nanowire, defined between entangled Ferromagnetic Domain Walls, and evaluate the Euclidean-time dependence of the domain wall width and angular momentum transfer at the domain walls, which has been recently proposed as a mechanism for Quantum Memory Storage.
Keywords: quantum; entanglement entropy; Ferromagnetic Domain Walls; solitons quantum; entanglement entropy; Ferromagnetic Domain Walls; solitons
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Crompton, P.R. The Quantum Noise of Ferromagnetic π-Bloch Domain Walls. Entropy 2009, 11, 548-559.

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