The Study Of Magnetoelectric Behavior Of RFe₂O₄(R=Lu,Yb And Tm) Multiferroic Oxides

Multiferroics,defined for those materials in which two or more properties of ferroelectricity,ferromagnetism and ferroelasticity coexist,have become one of the hottest research topics in material physics and condensed matter physics for the rich physical properties and wide application prospects.Multiferroic compounds can be divided into two categories:The ferroelectricity and ferromagnetism of the first type of multiferroic compounds have different origins and the coupling between them is very weak;The ferroelectricity of the second type of multiferroic compounds is induced by special magnetic structures and the coupling between ferroelectricity and ferromagnetism is much stronger.Both the charge and spin frustrated RFe₂O₄oxide belongs to the first type of multiferroic materials.In this paper,we have systematically investigated magnetic properties and dielectric properties of RFe₂O₄(R=Lu,Yb and Tm).The effects of different rare-earth ions R³⁺on the magnetic properties and dielectric properties of RFe₂O₄were discussed.In addition,the regulation of pulsed high magnetic field on the magnetic phase transitions of RFe₂O₄and Lu_1-xYb_xFe₂O₄(x=0,0.1,0.2 and 0.5)were studied.The details of research are shown as follows:(1)The research progress of RFe₂O₄oxides and doped Lu Fe₂O₄compound were introduced briefly from the aspects of crystal structure,magnetism,magnetoelectric coupling effect and dielectric properties.(2)The preparation and structural characteristics of RFe₂O₄(R=Lu,Yb and Tm)and Lu_1-xYb_xFe₂O₄polycrystalline samples were introduced.(3)The magnetization behaviors of Lu Fe₂O₄,Yb Fe₂O₄and Tm Fe₂O₄polycrystalline samples under the static state field and pulsed high magnetic field were investigated.Experimental results indicate that there is appearance of three interactions in Yb Fe₂O₄and Tm Fe₂O₄and the order of magnitude of them is:J(R³⁺-R³⁺)<J(R³⁺-Fe²⁺/Fe³⁺)<J(Fe²⁺/Fe³⁺-Fe²⁺/Fe³⁺).Based on the static state field and high field magnetization measurements,the magnetic phase diagrams(B-T)of Yb Fe₂O₄and Tm Fe₂O₄were constructed.In addition,the dielectric properties of the Yb Fe₂O₄and Tm Fe₂O₄polycrystalline samples were studied.It is found that the data of impedance and dielectric constant had a good correspondence with the magnetization data,which indicate the existence of magnetoelectric coupling effect in this system.(4)The magnetization behaviors of Lu_1-xYb_xFe₂O₄polycrystalline samples under static state field and pulsed high magnetic field were investigated.The experimental results show that Yb³⁺doping levels in Lu Fe₂O₄have influence on the magnetic interaction between Fe²⁺/Fe³⁺ions.Moreover,the magnetic phase transitions,dielectric constant and activation energy also can be regulated by changing the Yb³⁺doping concentration.