The Magnetic And Electrical Properties Of A New Diluted Magnetic Semiconductor LiZnX(X=N,P)

Dilute magnetic semiconductor,with both magnetic and electrical properties,satisfies the electron spin condition.It has been widely applied in spintronics and optoelectronics.The new I-II-V based dilute magnetic semiconductors realize the separation of the charge spin injection mechanism,and make it possible to study the influence of the carrier concentration or the spin concentration on the ferromagnetism.Moreover,it can be made into bulk materials,which provides conditions for studying their magnetic mechanism by means of nuclear magnetic resonance,neutron scattering and other microscopic magnetic measurements.In this work,Firstly,the first-principles principle is used to calculate the magnetoelectric and electrical properties of Cr-doped I-II-V semiconductor Li ZnP and Mn doped I-II-V semiconductor LiZnN.The bulk materials of Mn doped LiZnP and Cr doped LiZnP were prepared by high temperature solid phase synthesis,their microstructures,magnetic properties and electrical properties have been studied.The main results are as follows:?1?The band structure,electronic density and optical properties of the novel dilute magnetic semiconductor Li_1±y(Zn_1-xCr_x)P?x=0.0625,y=0.0625?are studied by the first principle.The incorporation of Cr induces sp-d orbital hybridization of Cr3d with Li2s and P3p,producing a spin-polarized impurity band,and the material exhibits semi-metal ferromagnetism.In the Li vacancy system,the band gap increases,the hybrid effect decreases and the net magnetic moment decreases.In the Li excess system,the system only exhibits semiconductor properties,and the energy gap decreases and the electrical conductivity increases.So the separation of spin and charge injection mechanisms may be achieved in LiZnP semiconductor.Through the comparison of optical properties,it is found that there is a new dielectric peak appears in the low-energy region of the dielectric function,and the absorption of the low frequency electromagnetic wave is improved.?2?The Li ZnP and Li?Zn,Mn?P bulk materials were successfully prepared by high temperature solid phase method.The study shows that LiZnP is a surface centered cubic structure,the space group is F-43m,and the band gap value is 2.03 eV.The doping of Mn did not change the crystal structure of Li ZnP,but the lattice constant of the sample increased as the doping amount increased.Electrical measurement shows that the Li?Zn,Mn?P system still behaves as a semiconductor.Magnetic measurements show that Mn doping can make the system produce magnetic,but the sample is easily oxidized and hydrolyzed to produce a strong magnetic MnP heterozygous phase.?3?The Li?Zn,Cr?P bulk materials were successfully prepared by high temperature solid-state method.The study of Li_1.1(Zn_1-xCr_x)P series found that the doping system is still cubic crystal structure,the space group is F-43m,and the lattice constant decreases with the increase of Cr doping concentration.The magnetic study found that the transition temperature of Li_1.1(Zn_0.85Cr_0.15)P can reach 270 K and the coercive force reaches 280 Oe,The electrical measurement shows that Li_1.1(Zn_1-xCr_x)P is still P-type semiconductor.?4?The first principle to calculate the magnetic and electrical properties of Li_1±y(Zn_1-xMn_x)N?x=0.0625,y=0.0625?.The results showed that the incorporation of Mn caused the system to generate spin-polarized impurity bands and exhibited semi-metallic ferromagnetism.In the Li vacancy system,The system is semi-metallic and has the most stable structure.In the Li excess system,the system is metallic and the electrical conductivity is enhanced.It shows that LiZnN semiconductors can achieve the separation of spin and charge injection mechanism.It is found by Heisenberg model that the Li vacancy system can increase the Curie temperature,and the Curie temperature can reach 575 K.