Magnetic Properties Of Molecular Magnets Based On Multi-metal Complexes By Cyanides

Molecular-based magnet is one of magnetic material which is composed of molecules or ions, they can be synthesized by conventional organic or inorganic chemical methods. Currently, the research, design and preparation of the molecule-based level mainly lies in the molecule magnetic material and organic elements. Because its synthesis preparation condition is moderate, compared with previous ionic and alloy magnet ,and can be obtained through the solution method. it has attracted considerable attention to complexs which can be assembled by two spin carrier which one contains magnetic of transition metal ion or rare earth metal ions ,and another contains magnetic of organic free radical groups. Additionally, the unlimited of molecular synthesis and the diversity of selection can bring a big breakthrough in the field of magnetic materials. In this thesis, the M?ssbauer measurements, magnetic measurements and structural measurements are performed to study the magnetic properties, microstructure and magnetic coupling mechanism in molecular magnets based on transition metal complexes. We discover the spin-glass-state for the first time in Ni1.125Co0.375[Fe(CN)6]·6.8H2O, which is also confirmed reasonably in terms of the qualitative & quantitive analysis. In the thesis, we have obtained the results in the following three aspects:1,A multimetallic Prussian blue compound Ni1.125Co0.375[Fe(CN)6]·6.8H2O was prepared by co-precipitation. A transition temperature from ferromagnetic to paramagnetic is about 16K , paramagnetic Curie temperature is 16.508±0.04K, and Curie constant C=3.024±0.03 emu.K/mol/Oe. The room temperature mossbauer spectrum and the infrared spectrum indicated that the metallic ions are bonded through cyanide ligand, i.e.: FeⅢ(s=1/2)-CN-(CoⅡ/NiⅡ)(96%) and FeⅢ(s=5/2)-NC-(CoⅡ/NiⅡ) (4%).2,The measurement of direct-current and alternating-current magnetic susceptibility indicated that the spin-glass-state exists in the Ni1.125Co0.375[Fe(CN)6]·6.8H2O. The dependence of peak position (Tf) on the frequency shift is also found with the fitting constant C=0.0081, by extrapolation under the zero frequency system's freezing temperatures is Tg=13.289K. Simultaneously we have gotten the characteristic time constantτ0=5.62×10-11s and judgment factor zv=5.4439.3,A 4f-3d cyanide ligand complex [FeGd(bipy)(H2O)4(CN)6]·5.69H2O was synthesized, which is executed on direct-current and alternating-current magnetization process. The analysis belongs to intramolecular ferromagnetic interaction in 300K-90K, about crystalline field effects or spin-crossover in 90K-50K and intermolecular antiferromagnetic interaction below 50K. At the same time, the alternating-current magnetic susceptibility indicated that magnetic ordering didn't exist the complex.At last, we summarize the work in the thesis and discuss the prospects of the study of molecular magnets based on multi metal complexes by cyanides.