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Entropy in Spin Relaxation, Spintronics, and Magnetic Resonance
Author(s) -
Csősz Gábor,
Dóra Balázs,
Simon Ferenc
Publication year - 2020
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.202000301
Subject(s) - von neumann entropy , entropy (arrow of time) , physics , statistical physics , time evolution , boltzmann constant , spin echo , spintronics , condensed matter physics , quantum mechanics , magnetic resonance imaging , ferromagnetism , quantum entanglement , medicine , quantum , radiology
The entropy change during spin relaxation for a realistic model system is studied, whose spin dynamics can be handled with the Boltzmann equation. The time evolution of the von Neumann entropy is monitored during the process and is compared with the recently introduced concept of the Loschmidt echo envelope. The time evolution of the two quantities is remarkably similar which helps to distinguish reversible and irreversible changes to the ensemble spin state. The method is also demonstrated for a toy model of nuclear magnetic resonance, where the usual π spin echo is performed numerically, and the echo envelope also follows the time evolution of the von Neumann entropy. The numerical approach highlights the utility of the entropy concept in analyzing various processes which occur during spin relaxation.