Narrow Results

We investigate the time evolution of the local spin in a molecular magnet interacting with injected electrons. By solving the time-dependent Schrödinger equations, we find that the variation in the magnetization of the molecular magnet and the electron spin crucially depends on the strength of the exchange interaction. We calculate the time evolution of the entanglement between the injected electron and the molecular magnet. It is found that the entanglement oscillates in time and the oscillations are closely related to the changes in the spins. The study provides an estimation of the feasibility of the encoding and read-out by using the polarization of the molecular magnets and the injected electrons.

A new approach to the magnetic hysteresis loop and magnetization relaxation of molecule magnet, Mn₁₂, is presented. The method, so called "quasi-thermal equilibrium (QTE) + erase phase (EP)" (QTE + EP), leads the dissipation in state evolution. The method gives an method to approach an irreversible quantum dynamic tunnelling and time evolution of system and straightly leads the hysteresis loops. The QTE can work well for the double-well system and is able to be extended to the multi-wells quantum system. The EP is based on the physics of random interaction with the environment that results the phase de-coherence or say "re-initial" of the phase of quantum state during the time evolution. The stairs in the magnetic loops of Mn₁₂ we have obtained quantitatively show the quantum resonant tunnelling. The relaxation of magnetization from initial lowest state is calculated for different temperatures and well shows the exponential behavior. The theoretical results well agree with the experiments.

Abundant asymmetric unit of the [FeBr₄]₂[py.H]₃Br magnetic molecule in the acetonitrile solvent was characterized via Debye function analysis (DFA) of the X-ray powder diffraction pattern from dilute solution. A diluted solution of the material in acetonitrile solvent has been prepared to reduce, as far as possible, the interaction between the molecular units. The X-ray diffraction from the sample was measured and Debye function simulations of three out of ten chemically plausible molecular units were observed to suitably comply with the experimental results. These three configurations were further optimized with first-principles method in the framework of density functional theory (DFT) and the most stable structure according to the calculated total energy is presented.

We study escape rate transitions in the Fe₈ molecular magnet with fourth-order transverse anisotropy in the presence of an external field perpendicular to the easy axis. Direct numerical diagonalization has been employed to investigate the transition type and the transition temperature T₀. We find that the first-order transition as well as the second-order transition can exist when the field is applied along the hard axis, while only the second-order transition appears for the field along the medium axis. It is also observed that the transition temperature is increased due to fourth-order transverse anisotropy.

Quantum dynamics time evolution of a molecular magnet Fe₈ interacting with an electron nuclear spin is studied by solving the time-dependent Schrödinger equations. It is found that the variation of Fe₈ magnetization and the nuclear spin crucially depends on the interaction strength. The time evolution of the entanglement between the injecting electron and Fe₈ is evaluated. It is observed that the entanglement oscillates in time and is tightly related to the spin variation of the injecting electron. From these characteristics, the technique for the reversing and read-out of Fe₈ spin states is suggested.

The magnetization of the prototypical molecular magnet Mn₁₂-acetate exhibits a series of sharp steps at low temperatures due to quantum tunneling at specific resonant values of magnetic field applied along the easy c-axis. An abrupt reversal of the magnetic moment of such a crystal can also occur as an avalanche, where the spin reversal proceeds along a "deflagration" front that travels through the sample at subsonic speed. In this article, we review experimental results that have been obtained for the ignition temperature and the speed of propagation of magnetic avalanches in molecular nanomagnets. Fits of the data with the theory of magnetic deflagration yield overall qualitative agreement. However, numerical discrepancies indicate that our understanding of these avalanches is incomplete.