Critical behavior in the itinerant ferromagnet SmMn_(2)Ge_(2)

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.

CrAlGe:An itinerant ferromagnet with strong tunability by heat treatment

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.

Giant Volume Magnetostriction Caused by Itinerant Electron Metamagnetic Transition and Pronounced Invar Effects in La(Fe_xSi_(1-x))_(13) Compounds

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.

Itinerant Topological Magnons in SU (2) Symmetric Topological Hubbard Models with Nearly Flat Electronic Bands

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.

Resistance Anomaly and Linear Magnetoresistance in Thin Flakes of Itinerant Ferromagnet Fe_(3)GeTe_(2)

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.

Quality of life and influencing factors between local and itinerant populations during the COVID-19 pandemic

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.

Around China in 80 Days (Ⅲ) On the road with itinerant Americans

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Stories of Itinerant Workers in Beijing

IANGXiangfenisacheerful19-year-oldpeasantgirl.Sheiscontentwithherlife,andfeelsasthoughshehasbeenlivingunderaluckystareversinceshegraduatedfromjuniormiddleschool.ShecomesfromasmallvillageinShandongProvince.HerwholefamilystilllivesinShandong,butWangnow...

Itinerant ferromagnetism entrenched by the anisotropy of spin-orbit coupling in a dipolar Fermi gas

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.

Magnetic properties and magnetic entropy changes of La1-xPrxFe11.5Si1.5 compounds with 0 ≤ x ≤ 0.5

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.

Magnetic properties, magnetoresistivity and magnetocaloric effect in Gd_xLa_(1-x)-MnSi alloys

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.

Magnetic and Transport Properties of La_(0.5-x)Nd_xBa_(0.5) CoO_3 Compounds

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.

Magnetic Phase Transition and Magnetic Entropy Change in La_(0.8)Pr_(0.2)Fe_(11.4)Si_(1.6) Compound

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.

通过调控范霍夫奇点在外延单层VSe_(2)中诱导出巡游铁磁性

处在费米能级处的范霍夫奇点(van Hove singularity)由于具有发散的态密度特征可以诱导出巡游铁磁性.本文在SrTiO_(3)(111)衬底上外延生长单层VSe_(2)薄膜,并通过调控范霍夫奇点诱导出巡游铁磁性.作者通过角分辨光电子能谱技术直接观测到了单层VSe_(2)中的范霍夫奇点能带结构.理论计算表明,当该范霍夫奇异点靠近费米能级时,可通过斯通纳(Stoner)不稳定性产生巡游铁磁性.实验上,作者利用SrTiO_(3)(111)在低温下极大增强的介电常数εr,通过界面电荷转移效应调控范霍夫奇点向费米能级处移动,并通过电输运测量观测到了3.3 K的巡游铁磁性转变.此外,通过改变薄膜层厚和更换衬底的方式,作者可以进一步调控界面电荷转移效果和范霍夫奇点的能量位置,并对巡游铁磁性进行调控.这项研究证明了范霍夫奇点可以成为巡游铁磁性的调控自由度,并拓展了二维磁体在未来电子信息技术的应用潜力.

Examining the Views and Opinions of Itinerary Traders on Adherence to COVID-19 Lockdown in Enugu State,Nigeria

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.

A New Theoretical Model for Calculation of Magneto-crystalline Anisotropy in R_2Fe_(14)B Series Compounds

1 Introduction The R2Fe14B 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 Nd2Fe14B and Pr2Fe14B have been made by many researchers using point charge model, but their results