The Preparation And Magnetic Properties Of TbPc₂ Single Molecular Magnet

Single molecular magnet is a kind of molecular-based magnetic materials,which exhibits slow relaxtion of magnetization at low temperature.Since the discovery of single molecular magnets,they have been investigated from the viewpoints of not only the basic sciences,due to the phenomena they exhibit,such as slow relaxation mechanisms and quantum tunneling of magnetization,but also the applied sciences,for use in next-generation devices,such as memory storage and quantum computers.Therefore,single molecular magnets become the research hoyspot in recent years.TbPc2 is among the most important single molecular magnets ever reported,due to its very high anisotropic barrier more than the others.However,its investigation in application field is seriously obscaled because of its quantum tunneling of magnetization which leads to very small magnetic remanence.In this study,the solvothermal synthesis scheme,purification method and magnetic properties of TbPc2 single molecule magnet were studied in detail.Meanwhile,we investgated the quantum tunneling of magnetization by using a double-well potential.YPc2 was also prepared by solvothermal method as a contrast.To further understand the effect of Ln-Ln dipole interaction on the magnetodynamic behavior,an amorphous TbPc2 thin film was prepared and studied.The main contents were discussed as follows.(1)LnPc2(Ln=Tb,Y)crystals was synthesized by a solvothermal method,and column chromatography was used to pure the product.The X-ray diffraction spectrum and fourier transform infrared spectroscopy experiments indicated that the purity was very high.The scanning electron microscope images showed that the TbPc2 crystals were plate-like with the size between 10 ?m and 50 ?m and the YPc2 crystals were fine platelets with the size between 1 ?m and 15 ?m.The magnetic hysteresis loops of TbPc2 powder indicated that TbPc2 exhibited magnetic hysteresis in the temperature range of 2 K?10 K.The loops decreased sharply at zero field beacause the quantum tunneling of magnetization.Then we analysised this effect by using a double-well model.YPc2 magnetic test proved its paramagnetic nature.(2)In order to clarify that the magnetism of TbPc2 was derived from the TbPc2 molecule itself or magnetic domains,we diluted TbPc2 into paramagnetic YPc2 by synthesizing Tb0.1Y0.9Pc2.The hysteresis loops of Tb0.1Y0.9Pc2 at 2 K and 4 K exhibit magnetic hysteresis,which proved the single molecular properties of TbPc2.Our investgation also showed that the dipole interaction had a significant effect on the magnetokinetic behavior.(3)The influence of different substrates on the crystallization state of TbPc2 films was investigated.The X-ray diffraction spectrum showed all the TbPc2 films were amorphous.The magnetization curve loops indicated the disappearance of magnetic hysteresis,which comfirmed the magnetodynamics could be affected by the stacking structure.The fraction of the TbPc2 powder sample extracted from the crucible before evaporating the film does not show any comparable magnetic hysteresis over the whole investigated temperature range.The crystal structure resulted to be changed from X-ray diffraction analysis.This result also proved the the magnetodynamics could be significantly affected by the stacking structure.