The Study Of The Correlation Between Microstructure And Electromagnetic For Fe-Site Doping CuFeO₂ System

Delafossite oxides CuFeO₂ material shows a magnetoelectric coupling due to the antiferromagnetic interactions between the Fe³⁺ions in the triangular lattice structure,and has attracted extensive attentions in recent years.While,its ferroelectricity is weak and the mechanism of magnetoelectric coupling for CuFeO₂ system is debatable issue yet.The study of the mechanism for magnetoelectric coupling has become a hot issue.Considering the unique property of Fe³⁺ions at the triangular lattice structure,the substitution at Fe site for CuFeO₂ system is carried out to investigate the influence of the characteristics?valence,size,magnetism and concentration?for doping ions on the microstructure and the electromagnetic property of the system.A series of experimental samples are prepared by standard solid state reactions,and the microstructure and electromagnetic property are characterized by means of X-ray diffractometer,Positron annihilation technique,Physical property measurement system and so on.The research contents are as follows:1.The effect of non-magnetic transition metals element Ti⁴⁺ions doped at Fe site on the microstructure and electromagnetic property for CuFeO₂ system are investigated.The experiment shows that the vibrational energy of the Fe-O bonds in the octahedral system and the Cu-O bonds near the adjacent lattices are changed by Gd doping.And the Gd doping has obvious influence upon the defect concentration,size and electronic structure of the samples;The formation of antiferromagnetic phase at low temperature is suppressed by Ti doping,and the magnetic transition temperature shifts to a low temperature region;The prepared samples with x=0-0.06 exhibit the giant dielectric property?>10³?.The study shows that the concentration and size of vacancy defects,the local electron density of the system are the important factors,which affects the magnetic property of the system;the microstructure has obvious influence on dielectric property for CuFeO₂ system.2.The effect of non-magnetic transition metals elements Ti⁴⁺/Zr⁴⁺/Hf⁴⁺ions with different ionic radius doped at Fe site on the microstructure and electromagnetic property for CuFeO₂ system are studied.The experiment shows that the Zr⁴⁺/Hf⁴⁺with larger ionic radius doping could lead to the lattice distortion for the CuFeO₂ system.The transition metal elements and doping concentrations have different effects on the morphology of the CuFeO₂system;Hf⁴⁺/Zr⁴⁺doping destroys the stability of antiferromagnetic quartic lattice,which makes the magnetic transition temperature shift to the lower temperature region;The giant dielectric property of CuFeO₂ system is suppressed by the transition metals elements doping.The study considers that the doping ions with large radius could cause the lattice distortion of the system,which changes the magnetic structure of the system and then affects the magnetic property of the system;The micromorphology of the system has an important effect on the dielectric property of the system.3.The effect of rare-earth magnetic Gd³⁺doping at Fe site on the microstructure and electromagnetic property of CuFeO₂ system is studied.The experiment shows that a small amount of Gd³⁺ion doping?x<0.07?could effectively occupy the Fe³⁺site in the lattice of CuFeO₂ system and promote the grain growth;Rare-earth doping has obvious effect on the magnetic phase transition of the system,in which no magnetic phase transition is observed in x?0.07 samples within the testing temperature range.The x=0.15 sample possesses the maximum magnetization?40 emu/g?;All the samples shows the giant dielectric property?¹0⁴?,and proper doping content can improve the dielectric property of the system.The study considers that Gd doping can effectively introduce the structure modulation,change the degree of frustration for the system,and then affect the magnetic property and dielectric property of the system.In this paper,the evolution of the microstructure?such as crystal structure,micro-morphology,electronic structure,defect characteristics?and the influence of characteristics for doping ion on the electromagnetic property of the system are investigated,which can provide the basic experimental data for the explanation of multiferroic machnism and application of the strong electron correlation system CuFeO₂.