A search was made for possible half-metallic(HM)antiferromagnet(AFM)in all the(C_(2)^(92)=406)double perovskites structures of Sr2BB′O6 where BB′pairs are any combination of 3d,4d or 5d transition elements with the ...A search was made for possible half-metallic(HM)antiferromagnet(AFM)in all the(C_(2)^(92)=406)double perovskites structures of Sr2BB′O6 where BB′pairs are any combination of 3d,4d or 5d transition elements with the exception of La.Sr can also be replaced by Ca or Ba whenever HM-AFM was found and similar calculations were then performed in order to probe further possibilities.It was found that A_(2)MoOsO_(6),A_(2)TcReO_(6),A_(2)CrRuO_(6),where A=Ca,Sr,Ba,are all potential candidates for HM-AFM.The AFM of A2BB′O6 comes from both the superexchange mechanism and the generalized double exchange mechanism via the B(t2g)-O2pp-B′(t2g)coupling,With the latter also being the origin of their HM.Also considered were the effects of spin-orbit coupling(SOC)and correlation(+U)by introducing+SOC and+U corrections.It is found that the SOC effect has much less influence than the correlation effect on the HMproperty of the compounds.For A_(2)TcReO_(6)and A_(2)CrRuO_(6),after+U,they become nearlyMott-Insulators.In the future,it is hoped that therewill be further experimental confirmation for these possible HM-AFMcandidates.展开更多
In this paper,we present calculations based on density functional theory using generalized gradient approximation(GGA)in double perovskite structure La_(2)BB'O_(6)(B,B'=3d transition metal)out of 45(C_(2)^(10)...In this paper,we present calculations based on density functional theory using generalized gradient approximation(GGA)in double perovskite structure La_(2)BB'O_(6)(B,B'=3d transition metal)out of 45(C_(2)^(10))combinational possibilities.Considering 4 types of magnetic states,namely,ferromagnetic(FM),ferrimagnetic(FiM),antiferromagnetics(AF),and nonmagnetic(NM)with full structure optimization,13 possible surviving,stable FM/FiM-HM materials containing 6 FM-HM materials(La_(2)ScNiO_(6),La_(2)CrCoO_(6),La_(2)CrNiO_(6),La_(2)VScO_(6),La_(2)VZnO_(6),and La_(2)VNiO_(6))and 7 FiM-HM materials(La_(2)VFeO_(6),La_(2)ZnCoO_(6),La_(2)TiCoO_(6),La_(2)CrZnO_(6),La_(2)CrMnO_(6),La_(2)ScFeO_(6),and La_(2)TiMnO_(6))are found.Considering the correlation effect(GGA+U),there are 6 possible half-metallic stable,surviving(HM)materials containing 3 FMHM materials(La_(2)ScNiO_(6),La_(2)CrCoO_(6),and La_(2)CrNiO_(6))and 3 FiM-HM materials(La_(2)VFeO_(6),La_(2)ZnCoO_(6),and La_(2)TiCoO_(6)).展开更多
Rollable photonic devices that can adapt to freeform surfaces with reduced dimensions while maintaining their original functionalities are highly desirable.Among photonic devices,metamaterials with hyperbolic dispersi...Rollable photonic devices that can adapt to freeform surfaces with reduced dimensions while maintaining their original functionalities are highly desirable.Among photonic devices,metamaterials with hyperbolic dispersion in momentum space,defined as hyperbolic metamaterial(HMM),possess a large photonic density of states that has been proven to boost light-matter interaction.However,these devices are mainly developed on rigid substrates,restricting their functionalities.Here,we present the attempt to integrate flexible and rollable HMMs consisting of polymer and metal multilayers on paper substrate.Quite interestingly,this design enables to exhibit high photonic density of states and scattering efficiency to enhance stimulated emission and induce pronounced laser action.The flexible and rollable HMM structure remains well its functionalities on freeform surfaces with curvature radius of 1 mm,and can withstand repeated bending without performance degradation.The intensity of laser action is enhanced by 3.5 times as compared to the flat surface.We anticipate that this flexible and rollable HMM structure can serve as a diverse platform for flexible photonic technologies,such as light-emitting devices,wearable optoelectronics,and optical communication.展开更多
基金supports received from the National Science Council(99B0320)the National Center for Theoretical Sciences(NCTS),South Taiwan.
文摘A search was made for possible half-metallic(HM)antiferromagnet(AFM)in all the(C_(2)^(92)=406)double perovskites structures of Sr2BB′O6 where BB′pairs are any combination of 3d,4d or 5d transition elements with the exception of La.Sr can also be replaced by Ca or Ba whenever HM-AFM was found and similar calculations were then performed in order to probe further possibilities.It was found that A_(2)MoOsO_(6),A_(2)TcReO_(6),A_(2)CrRuO_(6),where A=Ca,Sr,Ba,are all potential candidates for HM-AFM.The AFM of A2BB′O6 comes from both the superexchange mechanism and the generalized double exchange mechanism via the B(t2g)-O2pp-B′(t2g)coupling,With the latter also being the origin of their HM.Also considered were the effects of spin-orbit coupling(SOC)and correlation(+U)by introducing+SOC and+U corrections.It is found that the SOC effect has much less influence than the correlation effect on the HMproperty of the compounds.For A_(2)TcReO_(6)and A_(2)CrRuO_(6),after+U,they become nearlyMott-Insulators.In the future,it is hoped that therewill be further experimental confirmation for these possible HM-AFMcandidates.
基金the resource support from the Computational Materials Research Focus Group(CMRFG)the financial supports from the National Science Council(99B0320)+1 种基金the Center for General Education of National Normal Universitythe National Center for High-Performance Computing for computer time and facilities.
文摘In this paper,we present calculations based on density functional theory using generalized gradient approximation(GGA)in double perovskite structure La_(2)BB'O_(6)(B,B'=3d transition metal)out of 45(C_(2)^(10))combinational possibilities.Considering 4 types of magnetic states,namely,ferromagnetic(FM),ferrimagnetic(FiM),antiferromagnetics(AF),and nonmagnetic(NM)with full structure optimization,13 possible surviving,stable FM/FiM-HM materials containing 6 FM-HM materials(La_(2)ScNiO_(6),La_(2)CrCoO_(6),La_(2)CrNiO_(6),La_(2)VScO_(6),La_(2)VZnO_(6),and La_(2)VNiO_(6))and 7 FiM-HM materials(La_(2)VFeO_(6),La_(2)ZnCoO_(6),La_(2)TiCoO_(6),La_(2)CrZnO_(6),La_(2)CrMnO_(6),La_(2)ScFeO_(6),and La_(2)TiMnO_(6))are found.Considering the correlation effect(GGA+U),there are 6 possible half-metallic stable,surviving(HM)materials containing 3 FMHM materials(La_(2)ScNiO_(6),La_(2)CrCoO_(6),and La_(2)CrNiO_(6))and 3 FiM-HM materials(La_(2)VFeO_(6),La_(2)ZnCoO_(6),and La_(2)TiCoO_(6)).
基金This work was financially supported by the“Advanced Research Center for Green Materials Science and Technology”from The Featured Area Research Center Program within the framework of the Higher Education Sprout Project by the Ministry of Education(108L9006)the Ministry of Science and Technology in Taiwan(MOST 108-3017-F-002-002 and MOST 108-2112-M-002-019)H.I L.acknowledges fellowship support from the Ministry of Science and Technology Overseas Project for Post Graduate Research,Taiwan(108-2917-I-002-010).
文摘Rollable photonic devices that can adapt to freeform surfaces with reduced dimensions while maintaining their original functionalities are highly desirable.Among photonic devices,metamaterials with hyperbolic dispersion in momentum space,defined as hyperbolic metamaterial(HMM),possess a large photonic density of states that has been proven to boost light-matter interaction.However,these devices are mainly developed on rigid substrates,restricting their functionalities.Here,we present the attempt to integrate flexible and rollable HMMs consisting of polymer and metal multilayers on paper substrate.Quite interestingly,this design enables to exhibit high photonic density of states and scattering efficiency to enhance stimulated emission and induce pronounced laser action.The flexible and rollable HMM structure remains well its functionalities on freeform surfaces with curvature radius of 1 mm,and can withstand repeated bending without performance degradation.The intensity of laser action is enhanced by 3.5 times as compared to the flat surface.We anticipate that this flexible and rollable HMM structure can serve as a diverse platform for flexible photonic technologies,such as light-emitting devices,wearable optoelectronics,and optical communication.
