TiNi-based shape memory alloys have been extensively investigated due to their significant applications,but a comprehensive understanding of the evolution of electronic structure and electrical transport in a system w...TiNi-based shape memory alloys have been extensively investigated due to their significant applications,but a comprehensive understanding of the evolution of electronic structure and electrical transport in a system with martensitic transformations(MT) is still lacking.In this work,we focused on the electronic transport behavior of three phases in Ni_(50-x)Fe_xTi_(50)across the MT.A phase diagram of Ni_(50-x)Fe_xTi_(50) was established based on x-ray diffraction,calorimetric,magnetic,and electrical measurements.To reveal the driving force of MT,phonon softening was revealed using first-principles calculations.Notably,the transverse and longitudinal transport behavior changed significantly across the phase transition,which can be attributed to the reconstruction of electronic structures.This work promotes the understanding of phase transitions and demonstrates the sensitivity of electron transport to phase transition.展开更多
The lattice dynamics,elastic properties and the origin of vanished magnetism in equiatomic quaternary Heusler compounds CoMnVZ(Z=Al,Ga)are investigated by first principle calculations in this work.Due to the similar c...The lattice dynamics,elastic properties and the origin of vanished magnetism in equiatomic quaternary Heusler compounds CoMnVZ(Z=Al,Ga)are investigated by first principle calculations in this work.Due to the similar constituent atoms in CoMnVAl and CoMnVGa compounds,they are both stable in LiMgPdSn-type structure with comparable lattice size,phonon dispersions and electronic structures.Comparatively,we find that CoMnVAl is more structurally stable than CoMnVGa.Meanwhile,the increased covalent bonding component in CoMnVAl enhances its mechanical strength and Vickers hardness,which leads to better comprehensive mechanical properties than those of CoMnVGa.Practically and importantly,structural and chemical compatibilities at the interface make non-magnetic semiconductor CoMnVAl and magnetic topological semimetals Co2MnAl/Ga more suitable to be grown in heterostructures.Owing to atomic preferential occupation in CoMnVAl/Ga,the localized atoms Mn occupy C(0.5,0.5,0.5)Wyckoff site rather than B(0.25,0.25,0.25)and D(0.75,0.75,0.75)Wyckoff sites in LiMgPdSn-type structure,which results in symmetric band filling and consequently drives them to be non-magnetic.Correspondingly,by tuning localized atoms Mn to occupy B(0.25,0.25,0.25)or/and D(0.75,0.75,0.75)Wyckoff sites in off-stoichiometric Co-Mn-V-Al/Ga compounds and keeping the total valence electrons as 24,newly compensated ferrimagnetic compounds are theoretically achieved.We hope that our work will provide more choices for spintronic applications.展开更多
The hydrostatic pressure is expected to be an effective knob to tune the magnetostructural phase transitions of hexagonal MM’X alloys(M and M’denote transition metals and X represents main group elements).We perform...The hydrostatic pressure is expected to be an effective knob to tune the magnetostructural phase transitions of hexagonal MM’X alloys(M and M’denote transition metals and X represents main group elements).We perform magnetization measurements under hydrostatic pressure on an MM’X martensitic MnNi0.77Fe0.23Ge alloy.The magnetostructural transition temperature can be efficiently tuned to lower temperatures by applying moderate pressures,with a giant shift rate of-151 K/GPa.A temperature span of 30 K is obtained under the pressure,within which a large magnetic entropy change of-23 J·kg-1K-1 in a field change of 5 T is induced by the mechanical energy gain due to the large volume change.Meanwhile,a decoupling of structural and magnetic transitions is observed at low temperatures when the martensitic transition temperature is lower than the Curie temperature.These results show a multi-parameter tunable caloric effect that benefits the solid-state cooling.展开更多
基金supported by the State Key Development Program for Basic Research of China(Grant Nos.2019YFA0704900 and 2022YFA1403800)the Fundamental Science Center of the National Natural Science Foundation of China(Grant No.52088101)+2 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(CAS)(Grant No.XDB33000000)the Synergetic Extreme Condition User Facility(SECUF)the Scientific Instrument Developing Project of CAS(Grant No.ZDKYYQ20210003)。
文摘TiNi-based shape memory alloys have been extensively investigated due to their significant applications,but a comprehensive understanding of the evolution of electronic structure and electrical transport in a system with martensitic transformations(MT) is still lacking.In this work,we focused on the electronic transport behavior of three phases in Ni_(50-x)Fe_xTi_(50)across the MT.A phase diagram of Ni_(50-x)Fe_xTi_(50) was established based on x-ray diffraction,calorimetric,magnetic,and electrical measurements.To reveal the driving force of MT,phonon softening was revealed using first-principles calculations.Notably,the transverse and longitudinal transport behavior changed significantly across the phase transition,which can be attributed to the reconstruction of electronic structures.This work promotes the understanding of phase transitions and demonstrates the sensitivity of electron transport to phase transition.
基金Project supported by Special Fund for Introduced Talent to Initiate Scientific Research in Nanjing Tech Universitythe National Natural Science Foundation of China (Grant Nos. 51831003 and 51771225)
文摘The lattice dynamics,elastic properties and the origin of vanished magnetism in equiatomic quaternary Heusler compounds CoMnVZ(Z=Al,Ga)are investigated by first principle calculations in this work.Due to the similar constituent atoms in CoMnVAl and CoMnVGa compounds,they are both stable in LiMgPdSn-type structure with comparable lattice size,phonon dispersions and electronic structures.Comparatively,we find that CoMnVAl is more structurally stable than CoMnVGa.Meanwhile,the increased covalent bonding component in CoMnVAl enhances its mechanical strength and Vickers hardness,which leads to better comprehensive mechanical properties than those of CoMnVGa.Practically and importantly,structural and chemical compatibilities at the interface make non-magnetic semiconductor CoMnVAl and magnetic topological semimetals Co2MnAl/Ga more suitable to be grown in heterostructures.Owing to atomic preferential occupation in CoMnVAl/Ga,the localized atoms Mn occupy C(0.5,0.5,0.5)Wyckoff site rather than B(0.25,0.25,0.25)and D(0.75,0.75,0.75)Wyckoff sites in LiMgPdSn-type structure,which results in symmetric band filling and consequently drives them to be non-magnetic.Correspondingly,by tuning localized atoms Mn to occupy B(0.25,0.25,0.25)or/and D(0.75,0.75,0.75)Wyckoff sites in off-stoichiometric Co-Mn-V-Al/Ga compounds and keeping the total valence electrons as 24,newly compensated ferrimagnetic compounds are theoretically achieved.We hope that our work will provide more choices for spintronic applications.
基金Supported by the National Natural Science Foundation of China(Grant No.51722106)the National Key R&D Program of China(Grant No.2019YFA0704904)+1 种基金Users with Excellence Program of Hefei Science Center CAS(Grant No.2019HSC-UE009)Fujian Institute of Innovation,Chinese Academy of Sciences。
文摘The hydrostatic pressure is expected to be an effective knob to tune the magnetostructural phase transitions of hexagonal MM’X alloys(M and M’denote transition metals and X represents main group elements).We perform magnetization measurements under hydrostatic pressure on an MM’X martensitic MnNi0.77Fe0.23Ge alloy.The magnetostructural transition temperature can be efficiently tuned to lower temperatures by applying moderate pressures,with a giant shift rate of-151 K/GPa.A temperature span of 30 K is obtained under the pressure,within which a large magnetic entropy change of-23 J·kg-1K-1 in a field change of 5 T is induced by the mechanical energy gain due to the large volume change.Meanwhile,a decoupling of structural and magnetic transitions is observed at low temperatures when the martensitic transition temperature is lower than the Curie temperature.These results show a multi-parameter tunable caloric effect that benefits the solid-state cooling.
