First Principles Study On The Electronic Structure And Spin States Of Co Ions Of The LaCoO₃

With the rapid development of science and technology, mankind has entered the information age, theinformation storage and increasing demand, and develop more excellent performance, faster memory beCome the focus of attention. Perovsk ite manGanese oxide materials as represented by the Colossal magnetoresistance ef fect (CMR) has received widespread attention, and researchers in the perovskite C obalt oxide were also found in the CMR effect. The CMR effect in the perovskit e oxides have broad application prospects in the field of magnetic storage and se nsor, magnetic sensor, the read head can be made into thememory element, magn etoresistive tunneling junction. At the same time, in the external environment (suc h as temperature, magnetic field, doping) under different circuMStances, perovskit e Cobalt oxide will show differentproperties, the reason is that between Lattice an d orbital interactions involved, and the spin state transition for a long time there a re a lot of arguments, therefore, whether in theory or in the application of perovs kite Cobalt oxide material, is a topic worthy of study.In this paper, based on the first principles, using density functional theor y (DFT) pLane wave ultrasoft pseudopotential method, and selects the local densit y approximation (LDA) as the exchange CorreLationapproximation, the spin state of Co ions in LaCoO3 system and Ga, Ni doped LaCoO3 transformation of theener gy band structure, density of States, partial density of states calcuLated the energ y of the system, such as,analysis of the electronic structure and magnetic propert ies of Ga doped with LaCoO3, Ni, get the following results:(1) for the first transition metal oxides, in the use of CASTEP module, th e need for system is modified (+U), we read through the document, reference liter ature, finally selecting the appropriate value of U, the system canapproximate th e Gap value and literature.(2) the spin state change of Co ions in LaCoO3 (LSâ†'ISâ†'HS), the LaCoO3 system from the nonmagnetic insuLator to metal of the results, the reason is main ly because the electronic hybrid3d4s state and O state of 2s2p Co ion formation.(3) This chapter first principles calcuLation method using the pLane wave ultrasoft ps eudopotential and local spindensity approximation, the doped LaCo0.83Ga0.17O3 were optimiz ed, spin energy band structure and density of States, partial density of States and optical pro perties were calcuLated. Results show that the Ga doped LaCoO3, the 3d 2p state electrons a nd Co-O the p-d hybridization, the impurity band spin down through theFermi level, the syste m performance of the semi metallic, Compared with pure LaCoO3, the Conductivity increase s, at the same time due to the Co spin system with production and produced the net magnetic moment of 4.01 mu_B.And Ga is due to the inCorporation of La-0 bond is changed, the reason is also produce a netmagnetic moment of LaCo0.92Ga0.08O3 doped system. The dope d the imaginary part of the dielectric functionand the optical absorption spectra of the ne w peak appeared in the high energy region to high energy region,the absorption edge extensi on, the Complex refractive index function significant changes also occurred in thehigh energ y region, enhanced the system in the high frequency electromagnetic wave absorption ability.