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A new family of 3d–4f coordination polymers with the molecular formula [NiIILnIII(L)(dca)2(NO3)]n[Ln = Eu (1), Gd (2), Tb (3), Dy (4), and Ho (5); H2L = N,N′-bis(2-hydroxy-3-methoxy-5-methylbenzyl)homopiperazine; dca = dicyanamide] has been synthesized in search for new single-molecule magnet (SMM) materials containing highly anisotropic lanthanides. The magnetic properties of these materials have been established by DC and AC magnetometry and explained quantitatively by comprehensive phenomenological modeling based on a generalized Heisenberg-type model, hypothesized previously based on first-principles calculations. Single-crystal X-ray diffraction has shown that the compounds are isostructural, with lanthanide atoms occupying a nine-coordination site with muffin-like geometry and individual NiII–LnIIIunits linked by dca anions. Other than the paramagnetic compound 1, 2–5exhibit intra-unit ferromagnetic 3d–4f interactions, favorable for a large spin ground state. A slow field-induced relaxation of magnetization has been observed in compound 4(only), displaying a substantial energy barrier of Ueff/kB= 26.2(5) K, below 6 K. This is attributed to an easy-plane anisotropy and is consistent with the relaxation in systems with a Kramers ground state doublet and hyperfine interactions.

Room-temperature, long-range (300 nm), chirality-induced spin-selective electron conduction is found in chiral metal–organic Cu(II) phenylalanine crystals, using magnetic conductive-probe atomic force microscopy. These crystals are found to be also weakly ferromagnetic and ferroelectric. Notably, the observed ferromagnetism is thermally activated, so that the crystals are antiferromagnetic at low temperatures and become ferromagnetic above ∼50 K. Electron paramagnetic resonance measurements and density functional theory calculations suggest that these unusual magnetic properties result from indirect exchange interaction of the Cu(II) ions through the chiral lattice.

We present a comprehensive analysis of magnetic coupling in a group of three popular chromium-based molecular rings, the homometallic Cr8ring and the heterometallic Cr7Ni and Cr7Zn molecules. We show conclusively that the broken symmetry approach within density functional theory (DFT), based on suitable conventional or range-separated hybrid functionals, provides a quantitatively reliable tool to extract magnetic exchange coupling parameters in all rings considered, which opens a window for additional applications in molecular magnetism. We further show that a nonempirical model spin Hamiltonian, based on the parameters extracted from DFT, leads to excellent agreement with experimental susceptibility data and energy spectra. Moreover, based on an optimally tuned range-separated hybrid functional approach, we find that gas-phase gaps of the studied molecular rings are much larger than previously calculated and discuss the implications of the revised electronic structure to potential applications in molecular spintronics.

AbstractA numerical quantum transfer-matrix approach to S= 1 macroscopic chains with single-site anisotropy and alternating bonds is worked out in the framework of statistical mechanics. A fit of the experimental susceptibility data for a number of the quasi-one-dimensional molecular magnets is performed down to the low-temperature region. New microscopic parameters for the uniform as well as the non-uniform systems are established, and the temperature behaviour of the zero-field susceptibility for different ferro-antiferro coupling ratios is presented.

Abstract: The genetic algorithms in the variant developed earlier and in that improved by the mechanism of niches have been exploited in the analysis of global and local minima of the potential energy depending either on the inverse distance between particles (as in Coulomb interactions) or on the logarithm of this distance. The number N of point-charge particles is finite and they are confined by the parabolic potential. Solutions of the optimization problems yield for the ground-state configurations and a number of the metastable configurations as well as some saddle points. For the model with the logarithmic interactions, the new ground-state configuration is found for , whereas for the Coulomb model, some new configurations, observed earlier in the molecular dynamics simulations, are determined. [Copyright &y& Elsevier]