Transition metal and rare earth intermetallics have been a fertile playground for research of various quantum states.We report detailed magnetic studies on Sm Mn_(2)Ge_(2),an anisotropic itinerant magnet with multiple...Transition metal and rare earth intermetallics have been a fertile playground for research of various quantum states.We report detailed magnetic studies on Sm Mn_(2)Ge_(2),an anisotropic itinerant magnet with multiple magnetic phases.The critical behavior of the ferromagnetic phase transition is investigated by employing the modified Arrott plot with the Kouvel-Fisher method.The critical temperature TCis determined to be around 342.7 K with critical exponents ofβ=0.417 andγ=1.122,and the interaction function is found to be J(r)~r^(-4.68),suggesting the coexistence of long-range and shortrange magnetic interactions.Our results contribute to the understanding of complex magnetism in Sm Mn_(2)Ge_(2),which may provide fundamental guidance in future spintronic applications.展开更多
We present a comprehensive investigation on CrAlGe and realize that it is an itinerant ferromagnet with strong tunability of the Curie temperature T_(C)and the spontaneous momentμ_(0)depending on annealing heat treat...We present a comprehensive investigation on CrAlGe and realize that it is an itinerant ferromagnet with strong tunability of the Curie temperature T_(C)and the spontaneous momentμ_(0)depending on annealing heat treatment.While the value of T_(C) was previously reported to be 80 K withμ_(0)≈0.41μB,in this work the two quantities attain values as high as 170 K and 0.66μ_(B),respectively.Heat treatment does not cause changes of the lattice parameters and symmetry,but results in a slight narrowing of the Bragg peaks.The strong tunability of the itinerant ferromagnetism indicates significantly tunable hybridization between the Cr 3d electrons and the conduction bands,in agreement with the dominant Cr–Al/Ge bonds of this compound.Further tuning along the same line towards even stronger or weaker itinerant ferromagnetism promises an interesting follow-up to clarify the localized-itinerant duality of the 3d electrons in this compound.展开更多
A first-order itinerant electron metamagnetic (IEM) transition above the Curie temperature Tc for ferromagnetic La(Fe_xSi_1-x)13 compounds has been confirmed by applying magnetic field. The volume change just above T_...A first-order itinerant electron metamagnetic (IEM) transition above the Curie temperature Tc for ferromagnetic La(Fe_xSi_1-x)13 compounds has been confirmed by applying magnetic field. The volume change just above T_C for x=0.88 is huge of about 1.5%, which is caused by a large magnetic moment induced by the IEM transition. These compounds have a possibility for practical applications as giant magnetostrictive materials. Pronounced Invar effects bring about a negative thermal expansion below TC, closely correlated with the negative mode-mode coupling among spin fluctuations.展开更多
We show that a suitable combination of flat-band ferromagnetism,geometry and nontrivial electronic band topology can give rise to itinerant topological magnons.An SU(2) symmetric topological Hubbard model with nearly ...We show that a suitable combination of flat-band ferromagnetism,geometry and nontrivial electronic band topology can give rise to itinerant topological magnons.An SU(2) symmetric topological Hubbard model with nearly flat electronic bands,on a Kagome lattice,is considered as the prototype.This model exhibits ferromagnetic order when the lowest electronic band is half-filled.Using the numerical exact diagonalization method with a projection onto this nearly flat band,we can obtain the magnonic spectra.In the flat-band limit,the spectra exhibit distinct dispersions with Dirac points,similar to those of free electrons with isotropic hoppings,or a local spin magnet with pure ferromagnetic Heisenberg exchanges on the same geometry.Significantly,the non-flatness of the electronic band may induce a topological gap at the Dirac points,leading to a magnonic band with a nonzero Chern number.More intriguingly,this magnonic Chern number changes its sign when the topological index of the electronic band is reversed,suggesting that the nontrivial topology of the magnonic band is related to its underlying electronic band.Our work suggests interesting directions for the further exploration of,and searches for,itinerant topological magnons.展开更多
Research interests in recent years have expanded into quantum materials that display novel magnetism incorporating strong correlations,topological effects,and dimensional crossovers.Fe_(3)GeTe_(2)represents such a two...Research interests in recent years have expanded into quantum materials that display novel magnetism incorporating strong correlations,topological effects,and dimensional crossovers.Fe_(3)GeTe_(2)represents such a twodimensional van der Waals platform exhibiting itinerant ferromagnetism with many intriguing properties.Up to date,most electronic transport studies on Fe_(3)GeTe_(2)have been limited to its anomalous Hall responses while the longitudinal counterpart(such as magnetoresistance)remains largely unexplored.Here,we report a few unusual transport behaviors on thin flakes of Fe_(3)GeTe_(2).Upon cooling to the base temperature,the sample develops a resistivity upturn that shows a crossover from a marginally-ln T to a-T^(1/2)dependence,followed by a lowertemperature deviation.Moreover,we observe a negative and non-saturating linear magnetoresistance when the magnetization is parallel or antiparallel to the external magnetic field.The slope of the linear magnetoresistance also shows a nonmonotonic temperature dependence.We deduce an anomalous contribution to the magnetoresistance at low temperatures with a scaling function proportional-HT^(1/2),as well as a temperature-independent linear term.Possible mechanisms that could account for our observations are discussed.展开更多
Objective:To determine the difference in quality of life and its influencing factors between local and itinerant populations in Nanjing during COVID-19.Methods:The quality of life questionnaire,which was based on the ...Objective:To determine the difference in quality of life and its influencing factors between local and itinerant populations in Nanjing during COVID-19.Methods:The quality of life questionnaire,which was based on the Brief Scale of WHO Quality of Life and redesigned by the research group,was used to randomly investigate 1150 people in 5 districts of Nanjing.Results:A total of 1112 valid questionnaires were collected(local population,n=558;itinerant population,n=554).The quality of life of the itinerant population was significantly lower than the local population.The itinerant population scores in physiology,psychology,social relationships,and environment were lower than the local population(all P values<0.05).COVID-19 had a greater impact on the itinerant population than on the local population,especially in medical assistance,enjoyment of life,and interpersonal relationships(all P values<0.05).Conclusion:The itinerant population had a lower quality of life than that of the local population during the prevention and control pandemic of COVID-19,thus more social support and help is warranted.展开更多
We investigate the itinerant ferromagnetism in a dipolar Fermi atomic system with the anisotropic spin–orbit coupling(SOC),which is traditionally explored with isotropic contact interaction.We first study the ferroma...We investigate the itinerant ferromagnetism in a dipolar Fermi atomic system with the anisotropic spin–orbit coupling(SOC),which is traditionally explored with isotropic contact interaction.We first study the ferromagnetism transition boundaries and the properties of the ground states through the density and spin-flip distribution in momentum space,and we find that both the anisotropy and the magnitude of the SOC play an important role in this process.We propose a helpful scheme and a quantum control method which can be applied to conquering the difficulties of previous experimental observation of itinerant ferromagnetism.Our further study reveals that exotic Fermi surfaces and an abnormal phase region can exist in this system by controlling the anisotropy of SOC,which can provide constructive suggestions for the research and the application of a dipolar Fermi gas.Furthermore,we also calculate the ferromagnetism transition temperature and novel distributions in momentum space at finite temperature beyond the ground states from the perspective of experiment.展开更多
The anomalous Hall effect(AHE)that associated with the Berry curvature of occupied electronic states in momentum-space is one of the intriguing aspects in condensed matter physics,and provides an alternative for poten...The anomalous Hall effect(AHE)that associated with the Berry curvature of occupied electronic states in momentum-space is one of the intriguing aspects in condensed matter physics,and provides an alternative for potential applications in topological electronics.Previous experiments reported the tunable Berry curvature and the resulting magnetization switching process in the AHE based on strain engineering or chemical doping.However,the AHE modulation by these strategies are usually irreversible,making it difficult to realize switchable control of the AHE and the resultant spintronic applications.Here,we demonstrated the switchable control of the Berry-curvature-related AHE by electrical gating in itinerant ferromagnetic Cr_(7)Te_(8)with excellent ambient stability.The gate-tunable sign reversal of the AHE can be attributed to the redistribution of the Berry curvature in the band structure of Cr_(7)Te_(8)due to the intercalation-induced change in the Fermi level.Our work facilitates the applications of magnetic switchable devices based on gate-tunable Berry curvature.展开更多
Magnetic properties and magnetic entropy changes in LaFe11.5Si1.5 have been investigated by partially substituting Pr by La. It is found that La1-xPrxFe11.5Si1.5 compounds remain cubic NaZn13-type structures even when...Magnetic properties and magnetic entropy changes in LaFe11.5Si1.5 have been investigated by partially substituting Pr by La. It is found that La1-xPrxFe11.5Si1.5 compounds remain cubic NaZn13-type structures even when the Pr content is increased to 0.5, i.e. x = 0.5. Substitution of Pr for La leads to a reduction in both the crystal constant and the Curie temperature. A stepwise magnetic behaviour in the isothermal magnetization curves is observed, indicating that the characteristic of the itinerant electron metamagnetic （IEM） transition above Tc becomes more prominent with the Pr content increasing. As a result, the magnetic entropy change is remarkably enhanced from 23.0 to 29.4 J/kg·K as the field changes from 0 to 5T, with the value of x increasing from 0 to 0.5. It is more attractive that the magnetic entropy changes for all samples are shaped into high plateaus in a wide range of temperature, which is highly favourable for Ericsson-type magnetic refrigeration.展开更多
The results of magnetization, magnetoresistivity and magnetocalofic effect （MCE） studies performed on polycrystalline samples of the GdxLa1-xMnSi （x=0.5, 0.6, 0.7, 0.8, 0.9, 1.0） compounds were presented. Complex ...The results of magnetization, magnetoresistivity and magnetocalofic effect （MCE） studies performed on polycrystalline samples of the GdxLa1-xMnSi （x=0.5, 0.6, 0.7, 0.8, 0.9, 1.0） compounds were presented. Complex measurements were carried out on the GdxLa1-xMnSi compounds to determine the influence of substitution in the rare earth （R） sublattice on the magnetic and related properties of these compounds. The compounds with x≤0.6 demonstrated two magnetic phase transitions （ferromagnetic to paramagnetic and antiferro- magnetic to ferromagnetic） both of which were first order. Anomalies in the magnetocaloric effect, electroresistivity and magnetoresistivity were observed in the temperature ranges of the magnetic phase transitions. The temperature dependences of MCE and magnetoresistivity for these compounds correlated with the temperature dependence of magnetization.展开更多
Substituting effects of Nd for La in La 0.5 Ba 0.5 CoO 3 compounds were studied systematically. The results show that Nd doping does not change the itinerant properties of the Co3d electrons. The molecular ma...Substituting effects of Nd for La in La 0.5 Ba 0.5 CoO 3 compounds were studied systematically. The results show that Nd doping does not change the itinerant properties of the Co3d electrons. The molecular magnetic moment of the materials decreases monotonically with increasing Nd dopant. When Nd content x ≥0.45, a magnetic phase separation appears in the materials. When x ≤0.45, the Curie temperature decreases monotonically with increasing Nd dopant. This is due to the size effects of the rare earth ions. The electric resistance measurements show that in the studied temperature range, the conduction of the materials belongs to the thermo diffusion conduction below the Curie temperature, while it belongs to the variable range hopping conduction of polarons over the Curie temperature.展开更多
Moessbauer studies on the effect of substitution with 3% Al, Co, Mn atoms in the intermetallic compound of Hf0.8Ta0.2Fe2 are reported. The Al substitution leads to increase of the FM-AFM transition temperature and to ...Moessbauer studies on the effect of substitution with 3% Al, Co, Mn atoms in the intermetallic compound of Hf0.8Ta0.2Fe2 are reported. The Al substitution leads to increase of the FM-AFM transition temperature and to decrease of the AFM-PM transition temperature. The Co substitution leads to disappearance of the FM state, only showing some FM impurity component, while Mn substituted compound indicates coexistence of FM and AFM states at low temperature. The phenomena imply complex itinerant electron properties in these magnetic systems.展开更多
The magnetic properties and the phase transformation of the partial substitution of Pr for La in LaFe11.4Si1.6 have been investigated by the means of X-ray diffraction (XRD) and vibrating sample magnetic (VSM). The re...The magnetic properties and the phase transformation of the partial substitution of Pr for La in LaFe11.4Si1.6 have been investigated by the means of X-ray diffraction (XRD) and vibrating sample magnetic (VSM). The results indicated that the single phase NaZn13-type cubic structure is stabilized for the compound La0.8Pr0.2Fe11.4Si1.6 and large values of the isothermal magnetic entropy change SM around the curie temperature TC～194 K in relative low magnetic fields. The maximum value︱SM︱max～37.07 J/kg·K-1 under a field of 1.5 T. Such large MCEs are attributed to the sharp change of the magnetization at the Curie temperature, the field-induced IEM transition and a strong temperature dependence of the critical field BC.展开更多
The outbreak of COVID-19 caused human activities to be affected in one way or another.As a result,measures were put in place by various national governments to reduce the spread of the virus.This paper examines adhere...The outbreak of COVID-19 caused human activities to be affected in one way or another.As a result,measures were put in place by various national governments to reduce the spread of the virus.This paper examines adherence to COVID-19 guidelines in Nigeria among itinerant traders,using a total of 40 eligible participants from selected local governments in Enugu state,Nigeria.The study adapted purposive sampling techniques to identify eligible participants;while in-depth interview was the method used for data collection.Among other findings,result shows that the control measures rolled out by government were seriously undermined.Nomadic traders,driven by economic gains,played covert role in the spread of the virus.This signalled a weak link in the efforts to curb the spread of the virus in Nigeria.The study contributes to a more exact diagnosis of the weak link in the efforts to contain the spread of the virus and how the quest for economic gains drove the abuse of COVID-19 mitigation protocols with its attendant health implications.It therefore recommends that government should strengthen the institutional capacity for detection and control,and provide the critical infrastructural facilities that will make for intensified surveillance in future epidemic or pandemic outbreak.Economic incentives and the effective monitoring of protocol enforcers saddled with the responsibility of enforcing government directives are also encouraged in order to curb compromise.展开更多
1 Introduction The R<sub>2</sub>Fe<sub>14</sub>B type compound （R=rare earths）is an important kind of magnetic materials. One of its important features is that it has very strong magneto-crys...1 Introduction The R<sub>2</sub>Fe<sub>14</sub>B type compound （R=rare earths）is an important kind of magnetic materials. One of its important features is that it has very strong magneto-crystalline anisotropy,which exhibits very complex characteristics with different rare earth elements. The calculations of the magneto-crystalline anisotropy for compounds Nd<sub>2</sub>Fe<sub>14</sub>B and Pr<sub>2</sub>Fe<sub>14</sub>B have been made by many researchers using point charge model, but their results展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2021YFA1600204)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302802)+2 种基金the National Natural Science Foundation of China(Grant Nos.U1832214,U2032213,12104461,and 12074135)the High Magnetic Field Laboratory of Anhuisupported by the Start-up Project of Anhui University(Grant No.S020318001/020)。
文摘Transition metal and rare earth intermetallics have been a fertile playground for research of various quantum states.We report detailed magnetic studies on Sm Mn_(2)Ge_(2),an anisotropic itinerant magnet with multiple magnetic phases.The critical behavior of the ferromagnetic phase transition is investigated by employing the modified Arrott plot with the Kouvel-Fisher method.The critical temperature TCis determined to be around 342.7 K with critical exponents ofβ=0.417 andγ=1.122,and the interaction function is found to be J(r)~r^(-4.68),suggesting the coexistence of long-range and shortrange magnetic interactions.Our results contribute to the understanding of complex magnetism in Sm Mn_(2)Ge_(2),which may provide fundamental guidance in future spintronic applications.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52088101,11974389,and 12141002)the National Key Research and Development Program of China(Grant Nos.2021YFA0718702 and 2017YFA0303100)+1 种基金the Chinese Academy of Sciences through the Scientific Instrument Developing Project(Grant No.ZDKYYQ20210003)the Strategic Priority Research Program(Grant No.XDB33000000)。
文摘We present a comprehensive investigation on CrAlGe and realize that it is an itinerant ferromagnet with strong tunability of the Curie temperature T_(C)and the spontaneous momentμ_(0)depending on annealing heat treatment.While the value of T_(C) was previously reported to be 80 K withμ_(0)≈0.41μB,in this work the two quantities attain values as high as 170 K and 0.66μ_(B),respectively.Heat treatment does not cause changes of the lattice parameters and symmetry,but results in a slight narrowing of the Bragg peaks.The strong tunability of the itinerant ferromagnetism indicates significantly tunable hybridization between the Cr 3d electrons and the conduction bands,in agreement with the dominant Cr–Al/Ge bonds of this compound.Further tuning along the same line towards even stronger or weaker itinerant ferromagnetism promises an interesting follow-up to clarify the localized-itinerant duality of the 3d electrons in this compound.
基金Japanese Ministry of Education, Science, Sports and Culture!Grantin-Aid for Scientific Research (B)(2) 08455287
文摘A first-order itinerant electron metamagnetic (IEM) transition above the Curie temperature Tc for ferromagnetic La(Fe_xSi_1-x)13 compounds has been confirmed by applying magnetic field. The volume change just above T_C for x=0.88 is huge of about 1.5%, which is caused by a large magnetic moment induced by the IEM transition. These compounds have a possibility for practical applications as giant magnetostrictive materials. Pronounced Invar effects bring about a negative thermal expansion below TC, closely correlated with the negative mode-mode coupling among spin fluctuations.
基金Supported by the National Natural Science Foundation of China (Grant No.11774152)National Key R&D Program of China(Grant No.2016YFA0300401)。
文摘We show that a suitable combination of flat-band ferromagnetism,geometry and nontrivial electronic band topology can give rise to itinerant topological magnons.An SU(2) symmetric topological Hubbard model with nearly flat electronic bands,on a Kagome lattice,is considered as the prototype.This model exhibits ferromagnetic order when the lowest electronic band is half-filled.Using the numerical exact diagonalization method with a projection onto this nearly flat band,we can obtain the magnonic spectra.In the flat-band limit,the spectra exhibit distinct dispersions with Dirac points,similar to those of free electrons with isotropic hoppings,or a local spin magnet with pure ferromagnetic Heisenberg exchanges on the same geometry.Significantly,the non-flatness of the electronic band may induce a topological gap at the Dirac points,leading to a magnonic band with a nonzero Chern number.More intriguingly,this magnonic Chern number changes its sign when the topological index of the electronic band is reversed,suggesting that the nontrivial topology of the magnonic band is related to its underlying electronic band.Our work suggests interesting directions for the further exploration of,and searches for,itinerant topological magnons.
基金supported by the National Natural Science Foundation of China(Grant Nos.12174439,11961141011,U2032204,and 12074039)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDB28000000 and XDB33030000)。
文摘Research interests in recent years have expanded into quantum materials that display novel magnetism incorporating strong correlations,topological effects,and dimensional crossovers.Fe_(3)GeTe_(2)represents such a twodimensional van der Waals platform exhibiting itinerant ferromagnetism with many intriguing properties.Up to date,most electronic transport studies on Fe_(3)GeTe_(2)have been limited to its anomalous Hall responses while the longitudinal counterpart(such as magnetoresistance)remains largely unexplored.Here,we report a few unusual transport behaviors on thin flakes of Fe_(3)GeTe_(2).Upon cooling to the base temperature,the sample develops a resistivity upturn that shows a crossover from a marginally-ln T to a-T^(1/2)dependence,followed by a lowertemperature deviation.Moreover,we observe a negative and non-saturating linear magnetoresistance when the magnetization is parallel or antiparallel to the external magnetic field.The slope of the linear magnetoresistance also shows a nonmonotonic temperature dependence.We deduce an anomalous contribution to the magnetoresistance at low temperatures with a scaling function proportional-HT^(1/2),as well as a temperature-independent linear term.Possible mechanisms that could account for our observations are discussed.
基金This work is supported by National Natural Science Foundation of China(NO.82070093)511 Take-off Plan(Grant No.JSPH-511C-2018-10).
文摘Objective:To determine the difference in quality of life and its influencing factors between local and itinerant populations in Nanjing during COVID-19.Methods:The quality of life questionnaire,which was based on the Brief Scale of WHO Quality of Life and redesigned by the research group,was used to randomly investigate 1150 people in 5 districts of Nanjing.Results:A total of 1112 valid questionnaires were collected(local population,n=558;itinerant population,n=554).The quality of life of the itinerant population was significantly lower than the local population.The itinerant population scores in physiology,psychology,social relationships,and environment were lower than the local population(all P values<0.05).COVID-19 had a greater impact on the itinerant population than on the local population,especially in medical assistance,enjoyment of life,and interpersonal relationships(all P values<0.05).Conclusion:The itinerant population had a lower quality of life than that of the local population during the prevention and control pandemic of COVID-19,thus more social support and help is warranted.
基金supported by the National Key R&D Program of China(Grant Nos.2021YFA1400900,2021YFA0718300,and 2021YFA1400243)the Key Scientific Research Project of colleges and Universities in Henan Province(Nos.20A140018 and 23A140001)+1 种基金the National Natural Science Foundatiion of China(Grant Nos.12074105,12074106,12074120,12247146,12104135,and 61835013)the Natural Science Foundation of Shanghai(Grant No.20ZR1418500).
文摘We investigate the itinerant ferromagnetism in a dipolar Fermi atomic system with the anisotropic spin–orbit coupling(SOC),which is traditionally explored with isotropic contact interaction.We first study the ferromagnetism transition boundaries and the properties of the ground states through the density and spin-flip distribution in momentum space,and we find that both the anisotropy and the magnitude of the SOC play an important role in this process.We propose a helpful scheme and a quantum control method which can be applied to conquering the difficulties of previous experimental observation of itinerant ferromagnetism.Our further study reveals that exotic Fermi surfaces and an abnormal phase region can exist in this system by controlling the anisotropy of SOC,which can provide constructive suggestions for the research and the application of a dipolar Fermi gas.Furthermore,we also calculate the ferromagnetism transition temperature and novel distributions in momentum space at finite temperature beyond the ground states from the perspective of experiment.
基金National Natural Science Foundation of China,Grant/Award Numbers:92365203,52072168,51861145201,12204232,52302180,92064005National Key Research and Development Program of China,Grant/Award Numbers:2021YFA1601004,2021YFA1202901。
文摘The anomalous Hall effect(AHE)that associated with the Berry curvature of occupied electronic states in momentum-space is one of the intriguing aspects in condensed matter physics,and provides an alternative for potential applications in topological electronics.Previous experiments reported the tunable Berry curvature and the resulting magnetization switching process in the AHE based on strain engineering or chemical doping.However,the AHE modulation by these strategies are usually irreversible,making it difficult to realize switchable control of the AHE and the resultant spintronic applications.Here,we demonstrated the switchable control of the Berry-curvature-related AHE by electrical gating in itinerant ferromagnetic Cr_(7)Te_(8)with excellent ambient stability.The gate-tunable sign reversal of the AHE can be attributed to the redistribution of the Berry curvature in the band structure of Cr_(7)Te_(8)due to the intercalation-induced change in the Fermi level.Our work facilitates the applications of magnetic switchable devices based on gate-tunable Berry curvature.
基金Project supported by the National Natural Science Foundation of China （Grant No 50571112）, the National Basic Reseaxch Program of China （Grant No 2006CB601101） and the Program of Chinese Academy of Sciences （Grant No KJCX2-YW-W02）.
文摘Magnetic properties and magnetic entropy changes in LaFe11.5Si1.5 have been investigated by partially substituting Pr by La. It is found that La1-xPrxFe11.5Si1.5 compounds remain cubic NaZn13-type structures even when the Pr content is increased to 0.5, i.e. x = 0.5. Substitution of Pr for La leads to a reduction in both the crystal constant and the Curie temperature. A stepwise magnetic behaviour in the isothermal magnetization curves is observed, indicating that the characteristic of the itinerant electron metamagnetic （IEM） transition above Tc becomes more prominent with the Pr content increasing. As a result, the magnetic entropy change is remarkably enhanced from 23.0 to 29.4 J/kg·K as the field changes from 0 to 5T, with the value of x increasing from 0 to 0.5. It is more attractive that the magnetic entropy changes for all samples are shaped into high plateaus in a wide range of temperature, which is highly favourable for Ericsson-type magnetic refrigeration.
基金supported by the Federal Program on Support of Leading Scientific Schools (НШ-8701.2006.2)
文摘The results of magnetization, magnetoresistivity and magnetocalofic effect （MCE） studies performed on polycrystalline samples of the GdxLa1-xMnSi （x=0.5, 0.6, 0.7, 0.8, 0.9, 1.0） compounds were presented. Complex measurements were carried out on the GdxLa1-xMnSi compounds to determine the influence of substitution in the rare earth （R） sublattice on the magnetic and related properties of these compounds. The compounds with x≤0.6 demonstrated two magnetic phase transitions （ferromagnetic to paramagnetic and antiferro- magnetic to ferromagnetic） both of which were first order. Anomalies in the magnetocaloric effect, electroresistivity and magnetoresistivity were observed in the temperature ranges of the magnetic phase transitions. The temperature dependences of MCE and magnetoresistivity for these compounds correlated with the temperature dependence of magnetization.
文摘Substituting effects of Nd for La in La 0.5 Ba 0.5 CoO 3 compounds were studied systematically. The results show that Nd doping does not change the itinerant properties of the Co3d electrons. The molecular magnetic moment of the materials decreases monotonically with increasing Nd dopant. When Nd content x ≥0.45, a magnetic phase separation appears in the materials. When x ≤0.45, the Curie temperature decreases monotonically with increasing Nd dopant. This is due to the size effects of the rare earth ions. The electric resistance measurements show that in the studied temperature range, the conduction of the materials belongs to the thermo diffusion conduction below the Curie temperature, while it belongs to the variable range hopping conduction of polarons over the Curie temperature.
基金Supported by the National Natural Science Foundation of China under Grant No 20050284003.
文摘Moessbauer studies on the effect of substitution with 3% Al, Co, Mn atoms in the intermetallic compound of Hf0.8Ta0.2Fe2 are reported. The Al substitution leads to increase of the FM-AFM transition temperature and to decrease of the AFM-PM transition temperature. The Co substitution leads to disappearance of the FM state, only showing some FM impurity component, while Mn substituted compound indicates coexistence of FM and AFM states at low temperature. The phenomena imply complex itinerant electron properties in these magnetic systems.
基金Project supported by The National Natural Science Foundation of China (50164003)
文摘The magnetic properties and the phase transformation of the partial substitution of Pr for La in LaFe11.4Si1.6 have been investigated by the means of X-ray diffraction (XRD) and vibrating sample magnetic (VSM). The results indicated that the single phase NaZn13-type cubic structure is stabilized for the compound La0.8Pr0.2Fe11.4Si1.6 and large values of the isothermal magnetic entropy change SM around the curie temperature TC～194 K in relative low magnetic fields. The maximum value︱SM︱max～37.07 J/kg·K-1 under a field of 1.5 T. Such large MCEs are attributed to the sharp change of the magnetization at the Curie temperature, the field-induced IEM transition and a strong temperature dependence of the critical field BC.
基金supported by the National Key Research and Development Program of China(2018YFA0306800,2021YFA1400400,2018YFA0306200,and 2021YFA1202901)the National Natural Science Foundation of China(92165205,11790311,12004172,51861145201,52072168,21733001,and 91750101)+2 种基金the Innovation Program for Quantum Science and Technology for China(2021ZD0302803)the Jiangsu Planned Projects for Postdoctoral Research Funds(2020Z172)the Program of High-Level Entrepreneurial and Innovative Talents Introduction of Jiangsu Province,China。
文摘The outbreak of COVID-19 caused human activities to be affected in one way or another.As a result,measures were put in place by various national governments to reduce the spread of the virus.This paper examines adherence to COVID-19 guidelines in Nigeria among itinerant traders,using a total of 40 eligible participants from selected local governments in Enugu state,Nigeria.The study adapted purposive sampling techniques to identify eligible participants;while in-depth interview was the method used for data collection.Among other findings,result shows that the control measures rolled out by government were seriously undermined.Nomadic traders,driven by economic gains,played covert role in the spread of the virus.This signalled a weak link in the efforts to curb the spread of the virus in Nigeria.The study contributes to a more exact diagnosis of the weak link in the efforts to contain the spread of the virus and how the quest for economic gains drove the abuse of COVID-19 mitigation protocols with its attendant health implications.It therefore recommends that government should strengthen the institutional capacity for detection and control,and provide the critical infrastructural facilities that will make for intensified surveillance in future epidemic or pandemic outbreak.Economic incentives and the effective monitoring of protocol enforcers saddled with the responsibility of enforcing government directives are also encouraged in order to curb compromise.
文摘1 Introduction The R<sub>2</sub>Fe<sub>14</sub>B type compound （R=rare earths）is an important kind of magnetic materials. One of its important features is that it has very strong magneto-crystalline anisotropy,which exhibits very complex characteristics with different rare earth elements. The calculations of the magneto-crystalline anisotropy for compounds Nd<sub>2</sub>Fe<sub>14</sub>B and Pr<sub>2</sub>Fe<sub>14</sub>B have been made by many researchers using point charge model, but their results
