Analysis Of Several Molecular Magnetisms And The Research Of Effect Factors Of Neel Temperature

With the development of research in magnetism and magneticmaterials, molecular magnet has became an important branch inthis field, and played an important role in theory research and theexploration of materials, which has attracted attention from thechemist and physicist, biologists and materials scientists.In this article, we have used the Monte Carlo numericalsimulation method, studied the magnetic properties of molecularmagnetism[ Mn₂ （ N₃ ）₄ （ phen ）₂]_nand{FeL₂（μpz）}∞, and we have gotsome important magnetic parameters of molecular magnetism bythe method: land factor g and exchange coupling constant J, andhave drawn it’s spin configuration in different temperatures, andcalculated magnetisability curve of the different rates of exchangecoupling constant. At last, we discussed the three factors whichinfluence Neel temperature.First of all, we studied the relationship between magnetisabilitycurve for[ Mn₂（N₃）₄ （phen）₂]nand{FeL₂（μpz）}∞and temperaturechanging , worked out the good magnetic curve fit the experimentaldata well, even at low temperatures, we concluded that the MonteCarlo method is a powerful tool for studying molecular magnet,especially at low temperatures. Secondly, we have studied some magnetic properties of[NaMn （ox）（N₃）（H₂O）₄]_n, and given its land factor and exchange couplingconstant in theory. It is also found that the spin configuration tendsto be vertical at the low temperatures, and we have found that theirspin configuration is the ferromagnetic distribution in the horizontaldirection and the anti-ferromagnetic distribution in the verticaldirection at low temperatures. The conclusion has somesignificance for the experimental on studying the molecularmagnetism magnetic properties. We calculated magnetisabilitycurve with different values ofα=J 2 /J 1which are in [0, 1] range,found two—dimension honeycomb magnetic structure accord withany proportion exchange coupling constants, which provides theorybasis for exploring new molecular magnetism experimentally.Finally, we studied the three factors which influence high Neeltemperature by Monte Carlo:①If the orbitals match well with bridgeligand complexes based on symmetry;②the dimension ofcomplexes；③the spin quantum number of magnetic center. Wefound that the research results and expected are almost exactly thesame, The higher dimension of the molecular magnetism, the higherthe Neel temperature; the larger the center of the magnetic spinquantum number, the higher the Neel temperature; the strongerexchange coupling constant, the higher the Neel temperature.Either a single factor or several factors change, we found that thecalculation results match well with experimental dates . We alsoanalyzed three factors which affects the Neel temperature inqualitative analysis to find out the level to which theyaffect ,finding that the changing of exchange coupling constant is the first factor that influence the Neel temperature, the second isspin quantum number of magnetic center, the last isdimension .therefore , when we want to synthesize molecularmagnet, we should try to choose the better bridge ligand, thusimproving the Neel temperature largely.Thus, this provides theoretical basis for the synthesis of molecularmagnetism which have high Neel temperature.