Dynamics of molecular nanomagnets in time-dependent external magnetic fields: Beyond the Landau-Zener-Stückelberg model

P. Földi, M. Benedict, J. Milton Pereira, F. M. Peeters

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

The time evolution of the magnetization of a magnetic molecular crystal is obtained in an external time-dependent magnetic field, with sweep rates in the kT/s range. We present the "exact numerical" solution of the time-dependent Schrödinger equation, and show that the steps in the hysteresis curve can be described as a sequence of two-level transitions between adiabatic states. The multilevel nature of the problem causes the transition probabilities to deviate significantly from the predictions of the Landau-Zener-Stückelberg model. These calculations allow the introduction of an efficient approximation method that accurately reproduces the exact results. When including phase relaxation by means of an appropriate master equation, we observe an interplay between coherent dynamics and decoherence. This decreases the size of the magnetization steps at the transitions, but does not modify qualitatively the physical picture obtained without relaxation.

Original languageEnglish
Article number104430
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume75
Issue number10
DOIs
Publication statusPublished - Mar 29 2007

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Magnetization
Magnetic fields
Molecular crystals
magnetic fields
Hysteresis
magnetization
transition probabilities
hysteresis
causes
curves
predictions
approximation
crystals

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

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abstract = "The time evolution of the magnetization of a magnetic molecular crystal is obtained in an external time-dependent magnetic field, with sweep rates in the kT/s range. We present the {"}exact numerical{"} solution of the time-dependent Schr{\"o}dinger equation, and show that the steps in the hysteresis curve can be described as a sequence of two-level transitions between adiabatic states. The multilevel nature of the problem causes the transition probabilities to deviate significantly from the predictions of the Landau-Zener-St{\"u}ckelberg model. These calculations allow the introduction of an efficient approximation method that accurately reproduces the exact results. When including phase relaxation by means of an appropriate master equation, we observe an interplay between coherent dynamics and decoherence. This decreases the size of the magnetization steps at the transitions, but does not modify qualitatively the physical picture obtained without relaxation.",
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