Synthesis And Calculation Of The Optical Properties Of(La_1-xCa_x)(Cu_1-yMnySO System

Abstract:Diluted magnetic semiconductors with dual characteristics of spins and charges can be made into spintronic devices,which have a wide application in information transfer,processing and data store in modern society.In recent years,research on new diluted magnetic semiconductors with separate spins and charges based on iron-based superconductors system attracts more attention.In this dissertation,we synthesized new diluted magnetic semiconductors(La_1-xCa_x)(Cu_0.9Mn_0.1)SO(x=0.025?0.05?0.075?0.1and0.125)with separate spins and charges by means of solid-state-reaction methods,and measured and analysed the structural parameters and electromagnetic properties of the materials with the help of XRD,MPMS and PPMS.Meantime,we calculated the electronic structures(including band structure and DOS)and optical properties(such as reflection,absorption,complex dielectric function and energy loss spectrums)of La_0.75Ca_0.25Cu_0.75Mn_0.25SO system.The results are as follows.(1)We successfully synthesized new diluted magnetic semiconductors La_0.9Ca_0.1Cu_0.9Mn_0.1SO with Tc=125 and La_0.875Ca_0.125Cu_0.9Mn_0.1SO with Tc=130 in some way.It shows by structural analyses that the structural parameter a increases from3.9950nm to 3.9962nm with the Ca content addition in(La_1-xCa_x)(Cu_0.9Mn_0.1)SO(x=0.025?0.05?0.075?0.1 and 0.125).However,the structural parameter c decreases from 3.9962nm to 3.9950nm with the Ca content addition.It also shows by resistance measurements and analysis that the electrical resistivityincreaseswiththetemperaturedecreasingin(La_1-xCa_x)(Cu_0.9Mn_0.1)SO system.That is the electrical conductivity increases with Ca content addition.It indicates that the material presents good semiconductive properties.It also shows by magnetic measurements and analysis that the magnetization intensity gradually increases at first and then rapidly reduces when the dopants reach to a certain amount.It indicates that the ferromagnetism increases at first and then is suppressed.The Curie temperatures are 125K and 130K for(La_1-xCa_x)(Cu_0.9Mn_0.1)SO when x=0.1and 0.125,respectivily.(2)In the calculation part,the result is that La_0.75Ca_0.25Cu_0.75Mn_0.25SO is a direct gap semiconductor with the gap equal to 0.95e V.Compared with that in parent La Cu SO,all the sites of peaks of reflection,absorption,complex dielectric function and energy loss spectrums in La_0.75Ca_0.25Cu_0.75Mn_0.25SO have a“Red Shift”and the highest value of the peaks reduces a lot.It indicates that although the ferromagnetism is produced but the optical properties is reduced when doping by the separate spins and charges method.