Issue
EPL
Volume 87, Number 5, September 2009
Article Number 57010
Number of page(s) 6
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
DOI http://dx.doi.org/10.1209/0295-5075/87/57010
Published online 23 September 2009
EPL, 87 (2009) 57010
DOI: 10.1209/0295-5075/87/57010

Coherent spin rotation in the presence of a phonon-bottleneck effect

L. Chen and I. Chiorescu

Physics Department and the National High Magnetic Field Laboratory, Florida State University 1800 E. Paul Dirac Drive, Tallahassee, FL 32310, USA

ichiorescu@fsu.edu

received 28 May 2009; accepted in final form 28 August 2009; published September 2009
published online 23 September 2009

Abstract
A characteristic of spin reversal in the presence of phonon bottleneck is the deviation of the magnetization cycle from a reversible function into an opened hysteresis cycle. In recent experiments on molecular magnets (e.g.  ${\rm V}_{15}$ and ${\rm Ru}_{2}$), the zero-field level repulsion was sufficiently large to ensure an otherwise adiabatic passage through zero-field and the magnetization curves can be described by using only a phonon-bottleneck model. Here, we generalize the phonon-bottleneck model into a model able to blend the non-adiabatic dynamics of spins with the presence of a non-equilibrium phonon bath. In this simple phenomenological model, Bloch equations are written in the eigenbasis of the effective spin Hamiltonian, considered to be a two-level system at low temperatures. The relaxation term is given by the phonon-bottleneck mechanism. To the expense of calculus time, the method can be generalized to multi-level systems, where the notion of Bloch sphere does not apply but the density matrix formalism is still applicable.

PACS
75.45.+j - Macroscopic quantum phenomena in magnetic systems.
75.50.Xx - Molecular magnets.
75.10.Jm - Quantized spin models.

© EPLA 2009