Numerical modelling of coherent spin relaxation in nanomagnets, formed by
magnetic molecules of high spins, is accomplished. Such a coherent spin
dynamics can be realized in the presence of a resonant electric circuit coupled
to the magnet. Computer simulations for a system of a large number of
interacting spins is an efficient tool for studying the microscopic properties
of such systems. Coherent spin relaxation is an ultrafast process, with the
relaxation time that can be an order shorter than the transverse spin dephasing
time. The influence of different system parameters on the relaxation process is
analysed. The role of the sample geometry on the spin relaxation is
investigated.Comment: Latex file, 22 pages, 7 figure
The peculiarities of coherent spin radiation by magnetic nanomolecules is
investigated by means of numerical simulation. The consideration is based on a
microscopic Hamiltonian taking into account realistic dipole interactions.
Superradiance can be realized only when the molecular sample is coupled to a
resonant electric circuit. The feedback mechanism allows for the achievement of
a fast spin reversal time and large radiation intensity. The influence on the
level of radiation, caused by sample shape and orientation, is analysed. The
most powerful coherent radiation is found to occur for an elongated sample
directed along the resonator magnetic field.Comment: Latex file, 11 figure
Here we present results of our investigation of coherent efFects in polarized spin systems on the basis of a microscopic model but not using the phenomenological Bloch equations. A computer simulation is realized for a system of nuclear or electron spins interacting with realistic dipole-dipole forces. Di6'erent initial and external conditions are analyzed for a spin system coupled with a resonator or one without the resonator and in the presence of an external oscillating field or without this pumping. Insofar as the phenomenological equations presuppose the uniformity of a system, it requires a microscopic model to show accurately when the coherence does appear. To this end, we introduce the coherence coefficients and consider their time behavior in detail. Some peculiarities due to dipole spin interactions, which are not present in the Bloch equations, are noted.
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