Rational design of bifunctional electrocatalysts for oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)with excellent activity and stability is of great significance,since overall water splitting is a ...Rational design of bifunctional electrocatalysts for oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)with excellent activity and stability is of great significance,since overall water splitting is a promising technology for sustainable conversion of clean energy.However,most electrocatalysts do not simultaneously possess optimal HER/OER activities and their electrical conductivities are intrinsically low,which limit the development of overall water splitting.In this paper,a strategy of electric field treatment is proposed and applied to Ni/Co_(3)O_(4) film to develop a novel bifunctional electrocatalyst.After treated by electric field,the conductive channels consisting of oxygen vacancies are formed in the Co_(3)O_(4) film,which remarkably reduces the resistance of the system by almost 2×10^(4) times.Meanwhile,the surface Ni metal electrode is partially oxidized to nickel oxide,which enhances the catalytic activity.The electric-field-treated Ni/Co_(3)O_(4) material exhibits super outstanding performance of HER,OER,and overall water splitting,and the catalytic activity is significantly superior to the state-of-the-art noble metal catalysts(Pt/C,RuO_(2),and RuO_(2)‖Pt/C couple).This work provides an effective and feasible method for the development of novel and efficient bifunctional electrocatalyst,which is also promising for wide use in the field of catalysis.展开更多
Voltage control magnetism has been widely studied due to its potential applications in the next generation of information technology.PMN-PT,as a single crystal ferroelectric substrate,has been widely used in the study...Voltage control magnetism has been widely studied due to its potential applications in the next generation of information technology.PMN-PT,as a single crystal ferroelectric substrate,has been widely used in the study of voltage control magnetism because of its excellent piezoelectric properties.However,most of the research based on PMN-PT only studies the influence of a single tensile(or compressive)stress on the magnetic properties due to the asymmetry of strain.In this work,we show the effect of different strains on the magnetic anisotropy of an Fe_(19)Ni_(81)/(011)PMN-PT heterojunction.More importantly,the(011)cut PMN-PT generates non-volatile strain,which provides an advantage when investigating the voltage manipulation of RF/microwave magnetic devices.As a result,a ferromagnetic resonance field tunability of 70 Oe is induced in our sample by the non-volatile strain.Our results provide new possibilities for novel voltage adjustable RF/microwave magnetic devices and spintronic devices.展开更多
We report a perpendicular magnetic tunnel junction(p MTJ)cell with a tunnel magnetoresistance(TMR)ratio of nearly 200%at room temperature based on Co Fe B/Ta/Co Fe B as the free layer(FL)and a synthetic antiferromagne...We report a perpendicular magnetic tunnel junction(p MTJ)cell with a tunnel magnetoresistance(TMR)ratio of nearly 200%at room temperature based on Co Fe B/Ta/Co Fe B as the free layer(FL)and a synthetic antiferromagnetic(SAF)multilayer[Pt/Co]/Ru/[Pt/Co]/Ta/Co Fe B as the reference layer(RL).The field-driven magnetization switching measurements show that the p MTJs exhibit an anomalous TMR hysteresis loop.The spin-polarized layer Co Fe B of SAF-RL has a lower critical switching field than that of FL.The reason is related to the interlayer exchange coupling(IEC)through a moderately thick Ta spacer layer among SAF-RLs,which generates a moderate and negative bias magnetic field on Co Fe B of RL.However,the IEC among RLs has a negligible influence on the current-driven magnetization switching of FL and its magnetization dynamics.展开更多
Magnetoelectric(ME)coupling has attracted ever-increasing interest due to its novel physical mechanism and potential applications.One promising approach to attain the coupling between magnetic and electric orders conc...Magnetoelectric(ME)coupling has attracted ever-increasing interest due to its novel physical mechanism and potential applications.One promising approach to attain the coupling between magnetic and electric orders concerns the use of magnet/piezoelectric bilayer structures,in which展开更多
Molybdenum disulfide （MoS2） is an earth-abundant and low-cost hydrogen evolving electrocatalyst with the potential to replace traditional noble metal catalysts. The catalytic activity can be significantly enhanced a...Molybdenum disulfide （MoS2） is an earth-abundant and low-cost hydrogen evolving electrocatalyst with the potential to replace traditional noble metal catalysts. The catalytic activity can be significantly enhanced after modification due to higher conductivity and enriched active sites. However, the underlying mechanism of the influence of the resistance of electrode material and contact resistance on the hydrogen evolution reaction （HER） process is unclear. Herein, we present a systematic study to understand the relationship between HER performance and electrode conductivity, which is bi-tuned through the electric field and photoelectrical effect. It was found that the onset overpotential consistently decreased with the increase of electrode conductivity. In addition, the reduction of the contact resistance resulted in a quicker electrochemical reaction process than enhancing the conductivity of the MoS2 nanosheet. An onset overpotential of 89 mV was achieved under 60 mW/cm^2 sunlight illumination （0.6 sun） and a simultaneous gate voltage of 3 V. These physical strategies can also be applied to other catalysts, and offer new directions to improve HER catalytic performance of semiconductor materials.展开更多
In Ni-Mn-X（X=In,Sn,Sb） ferromagnetic shape memory alloys,a ferromagnetic transition from paramagnetic to ferromagnetic austenite and a martensitic transformation from ferromagnetic austenite to weak magnetic martens...In Ni-Mn-X（X=In,Sn,Sb） ferromagnetic shape memory alloys,a ferromagnetic transition from paramagnetic to ferromagnetic austenite and a martensitic transformation from ferromagnetic austenite to weak magnetic martensite occur in some particular composition ranges,in which abundant physical properties have been observed by the abrupt change of magnetization and resistivity around their transition temperatures in these alloys.Therefore,tuning the martensitic transformation temperature（TM） and enlarging the workingtemperature interval for Ni-Mn-X（X=In,Sn,Sb） alloys,are of great importance.In the present paper,we will focus on the effect of external factors,including pre-deformation,annealing,and high pressure annealing,on the magnetic transitions and the related magnetocaloric properties in Ni-Mn-Co-Sn ferromagnetic shape memory alloys.Our approaches and the main results in this particular field will be reviewed.展开更多
Epitaxial Ni–Mn–Ga thin films have promising application potential in micro-electro-mechanical sensing and actuation systems. To date, large abrupt magnetization changes have been observed in some epitaxial Ni–Mn–...Epitaxial Ni–Mn–Ga thin films have promising application potential in micro-electro-mechanical sensing and actuation systems. To date, large abrupt magnetization changes have been observed in some epitaxial Ni–Mn–Ga thin films, but their origin-either from magnetically induced martensite variant reorientation(MIR) or magnetic domain evolution-has been discussed controversially. In the present work, we investigated the evolutions of the magnetic domain and microstructure of a typical epitaxial Ni–Mn–Ga thin film through wide-field magneto-optical Kerr-microscopy. It is demonstrated that the abrupt magnetization changes in the hysteresis loops should be attributed to the magnetic domain evolution instead of the MIR.展开更多
The magnetic ground state switching between antiferromagnetic(AFM)and ferromagnetic(FM)states in EuTiO_(3)provides the feasibility of regulating its magnetic properties and magnetocaloric effect.First-principles calcu...The magnetic ground state switching between antiferromagnetic(AFM)and ferromagnetic(FM)states in EuTiO_(3)provides the feasibility of regulating its magnetic properties and magnetocaloric effect.First-principles calculations demonstrate that the magnetic ground states for EuTi_(0.875)Nb_(0.0625)Al_(0.0625)O_(3),EuTi_(0.8125)Nb_(0.125)Al_(0.)0_(625)O_(3),and EuTi_(0.75)Nb_(0.125)Al_(0.125)O_(3)are FM coupling.Experimental results also exhibit the FM coupling domination in these compounds,accompanied by a significantly enhanced low magnetic field magnetocaloric effect.The maximum magnetic entropy change of all the samples surpasses15 J kg^(-1)K^(-1)with a field change of 1 T.which is 1.4 times as large as that of bulk EuTiO_(3).Especially,the maximum refrigerating capacity for EuTi_(0.8125)Nb_(0.125)Al_(0.0625)O_(3)compound is evaluated to be 88.1 J kg^(-1),more than three times of that of EuTiO_(3).The remarkable magnetocaloric performances prove Nb and Al co-substituted EuTiO_(3)compounds to be competitive candidates for magnetic refrigeration in the liquid helium temperature regime.展开更多
1.Introduction Refrigeration plays an essential role in nowadays society.However,conventional refrigeration based on vapor compression cooling shows high energy consumption,complicated structure and even environmental...1.Introduction Refrigeration plays an essential role in nowadays society.However,conventional refrigeration based on vapor compression cooling shows high energy consumption,complicated structure and even environmental pollution.Searching for an environmentalfriendly and energy-saving refrigeration technology has become a matter of concern[1,2].In the past few decades,the solid-state refrigeration technologies mainly represented by magnetocaloric effect(MCE),electrocaloric effect(ECE)and elastocaloric effect(e CE)have been regarded as promising candidate to replace traditional vapor compression refrigeration technology owing to environmental friendliness and high efficiency[1-9].展开更多
基金supported by the program B for Outstanding PhD candidate of Nanjing University.
文摘Rational design of bifunctional electrocatalysts for oxygen evolution reaction(OER)and hydrogen evolution reaction(HER)with excellent activity and stability is of great significance,since overall water splitting is a promising technology for sustainable conversion of clean energy.However,most electrocatalysts do not simultaneously possess optimal HER/OER activities and their electrical conductivities are intrinsically low,which limit the development of overall water splitting.In this paper,a strategy of electric field treatment is proposed and applied to Ni/Co_(3)O_(4) film to develop a novel bifunctional electrocatalyst.After treated by electric field,the conductive channels consisting of oxygen vacancies are formed in the Co_(3)O_(4) film,which remarkably reduces the resistance of the system by almost 2×10^(4) times.Meanwhile,the surface Ni metal electrode is partially oxidized to nickel oxide,which enhances the catalytic activity.The electric-field-treated Ni/Co_(3)O_(4) material exhibits super outstanding performance of HER,OER,and overall water splitting,and the catalytic activity is significantly superior to the state-of-the-art noble metal catalysts(Pt/C,RuO_(2),and RuO_(2)‖Pt/C couple).This work provides an effective and feasible method for the development of novel and efficient bifunctional electrocatalyst,which is also promising for wide use in the field of catalysis.
文摘Voltage control magnetism has been widely studied due to its potential applications in the next generation of information technology.PMN-PT,as a single crystal ferroelectric substrate,has been widely used in the study of voltage control magnetism because of its excellent piezoelectric properties.However,most of the research based on PMN-PT only studies the influence of a single tensile(or compressive)stress on the magnetic properties due to the asymmetry of strain.In this work,we show the effect of different strains on the magnetic anisotropy of an Fe_(19)Ni_(81)/(011)PMN-PT heterojunction.More importantly,the(011)cut PMN-PT generates non-volatile strain,which provides an advantage when investigating the voltage manipulation of RF/microwave magnetic devices.As a result,a ferromagnetic resonance field tunability of 70 Oe is induced in our sample by the non-volatile strain.Our results provide new possibilities for novel voltage adjustable RF/microwave magnetic devices and spintronic devices.
基金Supported by the National Key Research and Development Program of China(Grant No.2016YFA0300803)the Open Research Fund of Jiangsu Provincial Key Laboratory for Nanotechnology+1 种基金the National Natural Science Foundation of China(Grant Nos.11774150 and 11874135)the Natural Science Foundation of Jiangsu Province of China(Grant No.BK20170627)。
文摘We report a perpendicular magnetic tunnel junction(p MTJ)cell with a tunnel magnetoresistance(TMR)ratio of nearly 200%at room temperature based on Co Fe B/Ta/Co Fe B as the free layer(FL)and a synthetic antiferromagnetic(SAF)multilayer[Pt/Co]/Ru/[Pt/Co]/Ta/Co Fe B as the reference layer(RL).The field-driven magnetization switching measurements show that the p MTJs exhibit an anomalous TMR hysteresis loop.The spin-polarized layer Co Fe B of SAF-RL has a lower critical switching field than that of FL.The reason is related to the interlayer exchange coupling(IEC)through a moderately thick Ta spacer layer among SAF-RLs,which generates a moderate and negative bias magnetic field on Co Fe B of RL.However,the IEC among RLs has a negligible influence on the current-driven magnetization switching of FL and its magnetization dynamics.
文摘Magnetoelectric(ME)coupling has attracted ever-increasing interest due to its novel physical mechanism and potential applications.One promising approach to attain the coupling between magnetic and electric orders concerns the use of magnet/piezoelectric bilayer structures,in which
文摘Molybdenum disulfide （MoS2） is an earth-abundant and low-cost hydrogen evolving electrocatalyst with the potential to replace traditional noble metal catalysts. The catalytic activity can be significantly enhanced after modification due to higher conductivity and enriched active sites. However, the underlying mechanism of the influence of the resistance of electrode material and contact resistance on the hydrogen evolution reaction （HER） process is unclear. Herein, we present a systematic study to understand the relationship between HER performance and electrode conductivity, which is bi-tuned through the electric field and photoelectrical effect. It was found that the onset overpotential consistently decreased with the increase of electrode conductivity. In addition, the reduction of the contact resistance resulted in a quicker electrochemical reaction process than enhancing the conductivity of the MoS2 nanosheet. An onset overpotential of 89 mV was achieved under 60 mW/cm^2 sunlight illumination （0.6 sun） and a simultaneous gate voltage of 3 V. These physical strategies can also be applied to other catalysts, and offer new directions to improve HER catalytic performance of semiconductor materials.
基金supported by the National Basic Research Program of China (No. 2005CB623605)the National Natural Science Foundation of China (Nos. 50701022and 50831006)+1 种基金Jiangxi Provincial Sci&Tech Project(No. 2010AZX00200)the Program for New Century Excellent Talents of China (No. NCET-08-0278)
文摘In Ni-Mn-X（X=In,Sn,Sb） ferromagnetic shape memory alloys,a ferromagnetic transition from paramagnetic to ferromagnetic austenite and a martensitic transformation from ferromagnetic austenite to weak magnetic martensite occur in some particular composition ranges,in which abundant physical properties have been observed by the abrupt change of magnetization and resistivity around their transition temperatures in these alloys.Therefore,tuning the martensitic transformation temperature（TM） and enlarging the workingtemperature interval for Ni-Mn-X（X=In,Sn,Sb） alloys,are of great importance.In the present paper,we will focus on the effect of external factors,including pre-deformation,annealing,and high pressure annealing,on the magnetic transitions and the related magnetocaloric properties in Ni-Mn-Co-Sn ferromagnetic shape memory alloys.Our approaches and the main results in this particular field will be reviewed.
基金supported by the National Natural Science Foundation of China (Grants Nos. 52071071)the Liaoning Revitalization Talents Program (Grant No. XLYC1802023)+1 种基金the Fundamental Research Funds for the Central Universities of China (Grant Nos. N2102006)the Program of Introducing Talents of Discipline Innovation to Universities 2.0 (the 111 Project of China 2.0, No. BP0719037)。
文摘Epitaxial Ni–Mn–Ga thin films have promising application potential in micro-electro-mechanical sensing and actuation systems. To date, large abrupt magnetization changes have been observed in some epitaxial Ni–Mn–Ga thin films, but their origin-either from magnetically induced martensite variant reorientation(MIR) or magnetic domain evolution-has been discussed controversially. In the present work, we investigated the evolutions of the magnetic domain and microstructure of a typical epitaxial Ni–Mn–Ga thin film through wide-field magneto-optical Kerr-microscopy. It is demonstrated that the abrupt magnetization changes in the hysteresis loops should be attributed to the magnetic domain evolution instead of the MIR.
基金supported financially by National Key R&D Program of China(No.2021YFB3501204)the National Science Fund for Distinguished Young Scholars(No.51925605)+2 种基金the National Natural Science Foundation of China(Nos.52171195 and 52171054)the Basic Frontier Scientific Research Program of Chinese Academyof Sciences From 0 to 1 Original Innovation Project(No.ZDBS-LYJSC017)the Key Research Program of Chinese Academy of Sciences(No.ZDRW-CN-2021-3)。
文摘The magnetic ground state switching between antiferromagnetic(AFM)and ferromagnetic(FM)states in EuTiO_(3)provides the feasibility of regulating its magnetic properties and magnetocaloric effect.First-principles calculations demonstrate that the magnetic ground states for EuTi_(0.875)Nb_(0.0625)Al_(0.0625)O_(3),EuTi_(0.8125)Nb_(0.125)Al_(0.)0_(625)O_(3),and EuTi_(0.75)Nb_(0.125)Al_(0.125)O_(3)are FM coupling.Experimental results also exhibit the FM coupling domination in these compounds,accompanied by a significantly enhanced low magnetic field magnetocaloric effect.The maximum magnetic entropy change of all the samples surpasses15 J kg^(-1)K^(-1)with a field change of 1 T.which is 1.4 times as large as that of bulk EuTiO_(3).Especially,the maximum refrigerating capacity for EuTi_(0.8125)Nb_(0.125)Al_(0.0625)O_(3)compound is evaluated to be 88.1 J kg^(-1),more than three times of that of EuTiO_(3).The remarkable magnetocaloric performances prove Nb and Al co-substituted EuTiO_(3)compounds to be competitive candidates for magnetic refrigeration in the liquid helium temperature regime.
基金supported by National Key R&D Program of China(Grant No.2017YFB0702701)the National Natural Science Foundation of China(Grant No.51771091,51976149)the Young Elite Scientists Sponsorship Program by CAST under the grant No.2019QNRC001。
文摘1.Introduction Refrigeration plays an essential role in nowadays society.However,conventional refrigeration based on vapor compression cooling shows high energy consumption,complicated structure and even environmental pollution.Searching for an environmentalfriendly and energy-saving refrigeration technology has become a matter of concern[1,2].In the past few decades,the solid-state refrigeration technologies mainly represented by magnetocaloric effect(MCE),electrocaloric effect(ECE)and elastocaloric effect(e CE)have been regarded as promising candidate to replace traditional vapor compression refrigeration technology owing to environmental friendliness and high efficiency[1-9].
