Studies On Diluted Magnetic Properties Based On The Antiferromagnetic Semiconductoe

The spintronic materials regarded as a series of new-type materials by using the spin and charge properties of electrons together are hopeful for designing devices with better performance.We used the first-principles method based on the density functional theory to study the magnetism,electronic structures,formation energy and Curie temperatures of the antiferromagnetic semiconductors SrTcO₃ and SrMnO₃ doped with partial transition metal elements.We studied the magnetism,electronic structures and formation energy of SrTcO₃doped with Mn at different concentrations,and calculated the Curie temperatures of these doped systems by using the Mean-Field-Theory.It is found that the incorporation of Mn atoms into SrTcO₃ can destroy the long-range ordering arrangement of the magnetic sublattices of SrTcO₃,eliciting diluted magnetism in those compounds.The magnetism is mainly originated from the strong orbital hybridization between Mn and Tc atoms.Meanwhile,it is found that the superexchange mechanism exists between the Mn,Tc and O atoms,and the O atom which is regarded as an intermediary can transmit magnetic moment between the Tc and Mn atoms.The doping of the Mn atoms can realize the transformation from the semiconductor state to metallic,spin-gapless semiconductor or half-metallic state of the electronic transport property.The calculated results of the Curie temperatures show that the higher the doping concentration of Mn element,the lower the Curie temperature,but all of the temperatures under small amount of dopant are far above the room temperature.We systematically studied the magnetism,electronic structures,formation energy and Curie temperatures of the SrTcO₃ doped with Fe and Co elements.It is found that the magnetic moments of the supercell of SrTc_1-xFe_xO₃?x=3.125%?and SrTc_1-xCo_xO₃?x=3.125%?are 1?_B and 2?_B,respectively.The hybridization between the Fe?Co?atom and Tc atoms induce the magnetism in those compounds.In the meantime,the spin polarization of the two series of compounds are relatively high.The calculated results of the Curie temperatures show that the doping of trace transition metal atoms can't change the magnetic transition temperature,obviously.We studied the electronic structures,formation energy,magnetism and Curie temperatures of partial transition metal atoms?TM=V,Cr,Tc,Fe,Co?doping the?-and?-SrMnO₃.We found that the formation energy of all the compounds are negative numbers,except for the compound doped with Co atom,indicating the thermodynamic stability in those compounds,and they are hopeful to be synthesized in experiment.The magnetic moments of the supercells of the doped compounds in?and?phases show some regularity,the values of the magnetic moments equal to the absolute of difference value between the proup-numbers of TM and Mn atoms.Meanwhile,the diluted magnetic property is mainly originate from the hybridization between the TM and Mn atoms.In addition,all the doping compounds exhibit half-metallic property.The calculated Curie temperatures of all the doping compounds are near the Néel temperature of SrMnO₃,and the Curie temperatures are relative to the redundant electrons or holes injected by the transition-metal-elements.