Effects Of Ion-doping On The Structure And Magnetic Properties Of YFeO₃

Yttrium ferrite?YFeO₃?is one of the typical rare earth perovskite ferrites,possessing unique magnetic properties with spin reorientation,Faraday rotation,etc.Its applications cover magnetic sensors,magneto-optic current sensors,optical converters,etc.Yttrium ferrite also has the potential as a single-phase multiferroic material.The application of YFeO₃ is closely related to its magnetic properties,so people have been actively exploring the structure and magnetic properties of YFeO₃.At present,there are few reports about the effects of A-site doping on the structure and magnetic properties of YFeO₃.And for pure-phase rare-earth perovskite ferrite RFeO₃,its structure and magnetic properties are related to degree of inclination of FeO₆ octahedron and Fe-O-Fe superexchange angle.What's more,the smaller the effective ion radius r(R³⁺)in the RFeO₃,the smaller the superexchange bond angle.This implies that changing the effective ionic radius of the Y site in YFeO₃ may also change the magnetic properties of YFeO₃,which can futher adjust the magnetic properties.In this paper,Nd,La,Dy single doped YFeO₃ samples and?Nd,Dy?,?Nd,La?,?Dy,La?,?Er,Nd?co-doped YFeO₃ samples were prepared by sol-gel method.The crystal structure and magnetic properties of the synthesized samples were characterized and analyzed by powder x-ray diffraction?XRD?,Fourier transform infrared spectroscopy?FT-IR?,scanning electron microscopy?SEM?,energy-dispersive x-ray?EDX?,and vibrating sample magnetometer?VSM?integrated in a physical property measurement system?PPMS-9?.The effects of doped ionic radius and concentration on the structure and magnetic properties of YFeO₃ were studied.The main results are as follows:1.Pure phase Y_1-xNd_xFeO₃?x=0.1,0.2,0.3,0.5,0.7,0.9,1??Y_1-xDy_xFeO₃?x=0.05,0.1,0.15,0.25,0.35,0.45,0.65,0.85,1??Y_1-xLa_xFeO₃?x=0,0.05,0.1,0.15,0.25,0.35,0.45,0.65,0.85,1??Y_0.5Er_0.5-xNd_xFeO₃?x=0,0.1,0.2,0.3,0.4?samples were synthesized by sol-gel method.The perovskite structure can still be maintained at higher doping concentrations.2.A series of Y_1-xNd_xFeO₃ samples have antiferromagnetism and weak ferromagnetism.With the concentration of Nd³⁺increases,the saturation magnetization firstly decreases and then increases and the residual magnetization decreases gradually while the coercive force firstly increases and then decreases.The change of magnetic properties of Y_1-xNd_xFeO₃samples is mainly caused by structural distortion due to Nd³⁺substitution of Y³⁺,which leads to changes of Fe-O-Fe superexchange effects and DM interactions.In addition,paramagnetic contribution caused by Nd³⁺spins and Nd³⁺-Fe³⁺interaction also have an effect on magnetic properties.3.A series of Y_1-xDy_x FeO₃ samples have antiferromagnetism and weak ferromagnetism.As the concentration of Dy³⁺increases,the saturation magnetization increases gradually,the residual magnetization firstly decreases,then increases,and decreases one more time.However,the coercive force decreases firstly and then increases.From x=0.25 to x=0.35,the coercivity decreases sharply.When x=0.45,the residual magnetization reaches a maximum value of 1.2063 emu·g^-1,and the coercive force reaches a minimum value of 129Oe.When x?0.85,the"waist"phenomenon disappeared.These changes of magnetic properties are mainly related to changes of the Fe-O-Fe superexchange effect and DM interactions caused by lattice distortion owing to Dy³⁺doping.In addition paramagnetic contribution caused by Dy ³⁺spins and Dy ³⁺-Fe³⁺interaction also have an effect on magnetic properties.4.With the increase of La³⁺concentration in a series of Y_1-xLa_xFeO₃ samples,the saturation magnetization and the residual magnetization gradually decrease,but the coercive force firstly increases and then decreases,and from x=0.65 to x=0.85,the coercive force decreases sharply.These changes of magnetic properties are mainly related to changes of Fe-O-Fe superexchange and changes in DM interaction caused by lattice distortion owing to La³⁺doping.5.With the increase of Nd³⁺doping content in Y_0.5Er_0.5-xNd_xFeO₃?x=0,0.1,0.2,0.3.0.4?,the coercivity increases gradually while the saturation magnetization and remanent magnetization decrease at the same time.Introducing Nd³⁺and Er³⁺ions into YFeO₃ will make a change on a structure distortion,resulting in the decrease of the Fe-O-Fe angle and the consequent reduction of superexchange effect.It has been found that the relationship between the r(R³⁺)and the superexchange bond angle obtained from the pure-phase rare-earth ferrite RFeO₃ may not be suitable for the doping system.The relationship between the r(R³⁺)and the superexchange bond angle in the doping system become more complicated.