V. K. Henner

Coherent spin relaxation in molecular magnets

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.

Coherent spin radiation by magnetic nanomolecules and nanoclusters

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.

Superradiation from crystals of high-spin molecular nanomagnets

Phenomenological theory of superradiation from crystals of high-spin molecules is suggested. We show that radiation friction can cause a superradiation pulse and investigate the role of magnetic anisotropy, external magnetic field, and dipole-dipole interactions. Depending on the contribution of all these factors at low temperature, several regimes of magnetization of crystal sample are described. Very fast switch of magnetizations direction for some sets of parameters is predicted.

Collective spin dynamics in magnetic nanomaterials

Magnetic nanomaterials are considered, forrned by magneitc nanomolecules with high spins. The problem of spin reversal in these materials is analysex, which is of interest for the possible use of such materials for quantum information processing and quantum cormputing. The fastest spin reversal can be achieved by coupling the spin sample to a resonant electric circuit and by an appropriate choice of the system parameters. A principal pont is to choose these parameters so that to organize coherent spin motion. Dynamics of collective motion is modelled by computer simulations, which confirm the high level of dynarinical coherence of molecular spins in the pricess of spin reversal.

Generation of coherent radiation by magnetization reversal in graphene

Local magnetic moments can be created in graphene by incorporating different defects. The possibility of regulating dynamics of magnetization in graphene, by employing the Purcell effect, is analyzed. The role of the system parameters in magnetization reversal is studied. The characteristics of such a reversal can be varied in a wide range, which can be used for various applications in spintronics. It is shown that fast magnetization reversal generates coherent radiation.

Spin superradiance by magnetic nanomolecules and nanoclusters

Spin dynamics of assemblies of magnetic nanomolecules and nanoclusters can be made coherent by inserting the sample into a coil of a resonant electric circuit. Coherence is organized through the arising feedback magnetic field of the coil. The coupling of a magnetic sample with a resonant circuit induces fast spin relaxation and coherent spin radiation, that is, superradiance. We consider spin dynamics described by a realistic Hamiltonian, typical of magnetic nanomolecules and nanoclusters. The role of magnetic anisotropy is studied. A special attention is paid to geometric effects related to the mutual orientation of the magnetic sample and resonator coil.