Narrow Results

Following an alternative version of Grover's algorithm, we propose a scheme to read- in information in Mn₁₂ molecular magnets with the help of multi-frequency magnetic pulses in two separate steps: first to realize an intermediate state |Ψ(T₁)> and then to reach the state |Ψ(T₂)> to encode information. All controllable parameters are calculated to implement read-in of information, and the durations of magnetic pulses are less than the dephasing time of quantum states in Mn₁₂. It is also shown that all the states of information can be initialized back to the intermediate state.

The authors theoretically investigate the formation of ultraslow dark and bright solitons via four-wave mixing (FWM) in a crystal of molecular magnets in the presence of a uniform d.c. magnetic field, where two strong continuous wave pump electromagnetic fields and a weak-pulsed probe electromagnetic field produce a pulsed FWM electromagnetic field. By solving the Maxwell–Schrödinger equations under the slowly varying envelope approximation and rotating-wave approximations, we demonstrate that both the weak-pulsed probe and FWM electromagnetic fields can evolve into dark and bright solitons with the same shape and the same ultraslow group velocity.

In this work, we elucidate the role of various microscopic interactions in high spin molecular nanomagnets. Starting from an effective spin Hamiltonian, we explain the origin and the importance of each coupling. We give special attention to exchange and dipole–dipole interactions between molecular magnets in a cubic lattice. The dispersion relation and magnetization behaviors are analyzed in the quantum magnons formalism taking into account the experimental reality and using common parameters values.

In this study, we have developed and used the advanced high-precision numerical techniques to accurately calculate the optical properties and spin structure, and access the details of spin dynamics of the cobalt octaethylporphyrin (CoOEP) in the THz pulse magnetic field. The optical spectra of CoOEP are calculated using first-principles based on the GW approximation. The optical properties, including complex dielectric function, optical reflectivity, extinction coefficient, refractive index and absorption coefficient up to 10 eV, together with the calculated spin structure are considered. The spin structure of CoOEP is described by means of the density of spin transitions within the terahertz range. The study covers both terahertz and visible ranges. On the basis of the obtained optical theoretical spectra and the spin structure of CoOEP, it can be concluded that the applied complex approach provides a detailed and accurate description of the optical properties of cobalt octaethylporphyrin within the whole range of energies.

A theoretical investigation of spin wave dynamics and scattering at a molecular junction between two Heisenberg ferromagnets is presented. The model system consists of two ferromagnetic ultrathin films with equal thickness of three atomic layers, joined together by a magnetic molecule. No electronic effects are considered, but local changes in the magnetic exchange field are assumed to be dominant. The mathematical framework of the matching method is used with nearest neighbor magnetic exchange interactions, to analyze both the spin fluctuation dynamics and the spin wave scattering phenomena at the junction boundary. The coherent reflection and transmission probabilities and the conductance of spin waves incident from the interior of the films onto the boundary are calculated in accordance with the Landauer–Büttiker formalism, and numerical results are presented for representative sets of system parameters for a large range of scattering frequencies. The scattered spectra show interesting sharp features, with associated Fano resonances, as a function of scattering frequencies, system parameters, and spin wave incidence angle. Moreover, a frequency selective conductance of the spin waves via Fano resonances can be obtained by an appropriate choice of the spin wave incident angle and system parameters.

The crystal structures and electronic and magnetic properties of conducting molecular magnets developed by our group are reviewed from the viewpoints of our two current strategies for increasing the efficiency of the π–d interaction. (EDTDM)₂FeBr₄ is composed of quasi-one-dimensional donor sheets sandwiched between magnetic anion sheets. The ground state of the donor layer changes from the insulator state to the metallic state by the application of pressure. When it is near to the insulator–metal phase boundary pressure, the magnetic order of the anion spins considerably affects the transport properties of the donor layer. The crystal structure of (EDO–TTFBr₂)₂FeX₄ (X = Cl, Br) is characterized by strong intermolecular halogen–halogen contacts between the organic donor and FeX₄ anion molecules. The presence of the magnetic order of the Fe₃₊ spins and relatively high magnetic order transition temperature proves the role of the halogen–halogen contacts as exchange interaction paths.

This work signifies the next step in our way in the magnetic properties simulation of spin clusters and extended networks containing quantum spins, by original FORTRAN codes based on Heisenberg–Dirac–VanVleck (HDVV) or Ising approaches, using Full Diagonalization Heisenberg Matrix (FDHM) or Monte Carlo–Metropolis (MCM) procedure, respectively.

We present the results of magnetic Monte Carlo studies on a magnetite type lattice, Ising model ferrimagnet that provide insight into the exchange interactions involved in Cubic Ferrospinels. We have demonstrated that a comparatively simple model can reproduce ferrimagnetic behavior of ferrospinels, particularly for magnetite.

We review recent progress in molecular magnets especially in the viewpoint of the application for quantum computing. After a brief introduction to single-molecule magnets (SMMs), a method for qubit manipulation by using non-equidistant spin sublevels of a SMM will be introduced. A weakly-coupled dimer of two SMMs is also a candidate for quantum computing, which shows no quantum tunneling of magnetization (QTM) at zero field. In the AF ring Cr₇Ni system, the large tunnel splitting is a great advantage to reduce decoherence during manipulation, which can be a possible candidate to realize quantum computer devices in future.

The crystal structures and electronic and magnetic properties of conducting molecular magnets developed by our group are reviewed from the viewpoints of our two current strategies for increasing the efficiency of the π–d interaction. (EDTDM)₂FeBr₄ is composed of quasi-one-dimensional donor sheets sandwiched between magnetic anion sheets. The ground state of the donor layer changes from the insulator state to the metallic state by the application of pressure. When it is near to the insulator-metal phase boundary pressure, the magnetic order of the anion spins considerably affects the transport properties of the donor layer. The crystal structure of (EDO–TTFBr₂)₂FeX₄ (X = Cl, Br) is characterized by strong intermolecular halogen-halogen contacts between the organic donor and FeX₄ anion molecules. The presence of the magnetic order of the Fe³⁺ spins and relatively high magnetic order transition temperature proves the role of the halogen-halogen contacts as exchange interaction paths.