Discovery of new potential magnetic semiconductors in quaternary Heusler compounds by addition of lanthanides

Magnetic semiconductors have attracted a lot of attention by having both electronic charge and spin degrees of freedom. In this paper, we obtained twenty magnetic semiconductors such as FeVLaSb, FeVPrSb, FeCrTbSi, CoVDySi, and CoVHoSi by adding lanthanides to quaternary Heusler compounds based on the Slater-Pauling law and orbital hybridization theory. The relationship between the lattice constants and energy gaps of the magnetic semiconductors with lanthanide elements is investigated by in-depth analysis. These magnetic semiconductors of quaternary Heusler compounds are promising candidates to find applications as spin filtering materials in spintronics devices.

Stability of Accretion Discs around Magnetized Stars

We study the stability of accretion disc around magnetised stars. Starting from the equations of magnetohydrodynamics we derive equations for linearized perturbation of geometrically thin, optically thick axisymmetric accretion disc with an internal dynamo around magnetized stars. The structure and evolution of such discs are governed by an evolution equation for matter surface density ∑(R,T). Using the time-dependent equations for an accretion disc we do a linear stability analysis of our steady disc solutions in the presence of the magnetic field generated due to an internal dynamo.

Advance in the chemical synthesis and magnetic properties of nanostructured rare-earth-based permanent magnets

Rare-earth-based permanent magnets are one of the most important magnets in both scientific and industrial fields. With the development of technology, nanostructured rarearth-based permanent magnets with high energy products are highly required. In this article, we will review the progress in chemical synthetic strategies of nanostructured rare-earth-based permanent magnets.

Magnetizing roast and magnetic separation of iron in rare-earth tailings

Magnetic separation of iron in rare-earth tailings was achieved by magnetizing roast process with coal as reductant. Effects of the temperature, carbon to oxygen ratio, and cooling type on magnetic susceptibility and composition of rare-earth tailings were investigated. The results show that roast conditions with the temperature of 650℃, carbon to oxygen ratio of 3.85, and holding time of 2.5 h are in favor of reduction of Fe_2O_3 to Fe_3O_4 when the roasted rare-earth tailings is cooled along with furnace. Under these roast conditions, magnetic susceptibility of rare-earth tailings is 2.36 that is very close to theoretical value（2.33）. However, magnetic separation results of iron in rare-earth tailings cooled along with furnace are not satisfactory. Through comparing magnetic separation results of iron in rare-earth tailings cooled by different ways, it is found that water cooling is more favored of magnetic separation of iron in the roasted rare-earth tailings than furnace cooling and air cooling. Grade and recovery of iron in concentrate from rare-earth tailings cooled by water are 45.00%-49.00% and 65.00%-77.50%, respectively.

Analytical Solutions for the Two-Dimensional Magnetic Fields in Disc-Type Permanent Magnet Machines

A two dimensional analytical method for predicting the magnetic field in the airgap/magnet region of a permanent magnet (PM) disc type machine is presented. The solutions of the governing field equations are given in both Cartesian and cylindrical coordinates. The expressions derived in this paper can be used conveniently for optimal design of machine. The computed results using the proposed 2D analytical method are validated by the more accurate, though a lot more complicated, 3D finite element analyses.

Temperature Profile of Black Hole Accretion Disc with Magnetic Coupling

Two new mapping relations between the angular coordinate on the black hole (BH) horizon and radialcoordinate on the disc are given according to the requirement of general relativity and Maxwell's equations, and theeffects of magnetic coupling (MC) on temperature of accretion disc are investigated by comparing with pure accretion.It is shown that the MC effects on the temperature profile are related intimately to the BH spin, and the influenceon the peak value of disc temperature based on the modified mapping relations is not as great as that based on thelinear mapping.The peak value and the corresponding radius of peak value ring of disc temperature do not increasemonotonically as the increasing spin of BH, each containing a maximum for the fast-spinning BH. The value ranges ofthe bolometric luminosity and color temperature of the disc are both extended by the MC effects.

Computational Design of Rare-Earth Reduced Permanent Magnets

Multiscale simulation is a key research tool in the quest for new permanent magnets.Starting with first principles methods,a sequence of simulation methods can be applied to calculate the maximum possible coercive field and expected energy density product of a magnet made from a novel magnetic material composition.Iron(Fe)-rich magnetic phases suitable for permanent magnets can be found by means of adaptive genetic algorithms.The intrinsic properties computed by ab initio simulations are used as input for micromagnetic simulations of the hysteresis properties of permanent magnets with a realistic structure.Using machine learning techniques,the magnet’s structure can be optimized so that the upper limits for coercivity and energy density product for a given phase can be estimated.Structure property relations of synthetic permanent magnets were computed for several candidate hard magnetic phases.The following pairs(coercive field(T),energy density product(kJ·m^-3))were obtained for iron-tin-antimony(Fe3Sn0.75Sb0.25):(0.49,290),L10-ordered iron-nickel(L10 FeNi):(1,400),cobalt-iron-tantalum(CoFe6Ta):(0.87,425),and manganese-aluminum(MnAl):(0.53,80).

Low temperature magnetism in the rare-earth perovskite GdScO3

The magnetic phase diagram of rare-earth perovskite compound,GdScO3,has been investigated by magnetization and heat capacity.The system undergoes an antiferromagnetic phase transition at TN=2.6 K,with an easy axis of magnetization along the a axis.The magnetization measurements show that it exists a spin-flop transition around 0.3 T for the applied field along the a axis.The critical magnetic field for the antiferromagnetic-to-paramagnetic transition is near 3.2 T when temperature approaches zero.By scaling susceptibilities,we presume this point(B=3.2 T,T=0 K)might be a fieldinduced quantum critical point and the magnetic critical fluctuations can even be felt above TN.

Influence of rare-earth ions on structural and magnetic properties of CdFe_2O_4 ferrites

Nano-sized powders of rare-earth ions added CdFe2O4 ferrites were synthesized by oxalate co-precipitation method.The influence of R ions（R = Sm3＋, Y3＋, and La3＋） on the microstructure and magnetic properties of CdFe2O4 ferrites was studied.XRD, SEM, FTIR, and magnetic hysteresis loops were used for analyzing the samples.The addition of R ions alters the structure of the powders and decreases the crystalline size, lattice constant, and grain size.The magnetic properties such as saturation magnetization, remanent magnetization, and magnetic moment increased due to addition of rare-earth ions in CdFe2O4 ferrite.The formation of secondary phase on the grain boundaries supports the abnormal growth.FTIR spectra show two absorption bands.Results suggest that the magnetic properties depend on the particular method of preparation and additives.

Design and Optimization of Line-Start Rare-Earth Permanent Magnetic Synchronous Motor Basing on FEM

The 2D transient FEM was used to analyze the starting process of the three phase rare-earth LS-PMSM.By verifying the simulation result with the experiment one, we get the conclusion that it is consistent with the experiment result very well.At the same time, by analyzing the situation of the magnetic bridge, we also get the result that the amplitude of EMF waves are changing with the situation of the magnetic poles and we can optimize the motor's structure at the same time.

Interplay of iron and rare-earth magnetic order in rare-earth iron pnictide superconductors under magnetic field

The magnetic properties of iron pnictide superconductors with magnetic rare-earth ions under strong magnetic field are investigated based on the cluster self-consistent field method. Starting from an effective Heisenberg model, we present the evolution of magnetic structures on magnetic field in RFeAsO（R = Ce, Pr, Nd, Sm, Gd, and Tb） and RFe_2As_2（R =Eu） compounds. It is found that spin-flop transition occurs in both rare-earth and iron layers under magnetic field, in good agreement with the experimental results. The interplay between rare-earth and iron spins plays a key role in the magneticfield-driven magnetic phase transition, which suggests that the rare-earth layers can modulate the magnetic behaviors of iron layers. In addition, the factors that affect the critical magnetic field for spin-flop transition are also discussed.

Study on Low Temperature Coefficient Rare-Earth Magnets

The rare-earth hard magnets with lower temperature coefficient, including Nd_2Fe_ 14B/Fe_3B-ferrite compound bonded magnets and Sm_ 0.8RE_ 0.2 (Co_ balFe_ 0.22Cu_ 0.06Zr_ 0.03)_ 7.4(RE=Gd, Er) sintered magnets, were studied. The result shows that the addition, that dope ferrite magnetic powder to double-phase nanocomposite Nd_2Fe_ 14B/Fe_3B magnetic powder, can make β_ jH_c to be obviously decreased. Similarly, the effect of homogeneous heating treatment on magnetic properties was studied. Doping heavy rare earth elements to the 2∶17-type SmCo magnet material powders shows that the sintered magnets obtained lower temperature coefficient, and enhanced magnets temperature stability.

Preparation of Rare-Earth Composite Ferrite Magnetic Fluid

Water-based rare-earth ferrite (Re xFe 3- xO 4)magnetic fluids were prepared by chemical co-precipitation method. The result shows that saturation magnetic intensity of ferrite magnetic fluids can be improved by adding Dy 3+ and the saturation magnetic intensity will reach the highest if n(Fe)∶n(Dy 3+ )=30∶1. The modification and formation mechanism of Re xFe 3- xO 4 particles is discussed in detail. The physicochemical properties are investigated by the Gouy magnetic balance, IR, TEM, XRD, and EDX, etc.

Permanent Rare-Earth Magnets—The Need to Protect Them against Corrosion

The RE-Fe-B permanent magnets have a complex microstructure and they are susceptible to corrosion process. In this paper, the commercial nickel coatings adhesion was investigated. The microstructure of the RE-Fe-B without coating was analyzed by scanning electronic microscopy and electrochemical techniques. The interface magnet/coating was studied by scanning electron microscopy and the nickel-plated Nd-Fe-B commercial magnets were tested in a salt spray chamber. The ferromagnetic and RE-rich phases were observed. After the anodic polarization curve, a strong intergranular corrosion was observed and the RE-rich phase was preferentially attacked. The interface magnet/Ni coating presented inter-granular corrosion that can affect the nickel coating adherence. This attack had probably occurred during the electrodeposition process. Not all the samples suffered localized corrosion during the salt spray tests and the Ni triple-layer coating presented a few corrosion points. RE-Fe-B alloy magnets need to be protected with appropriate coatings to each environment to which they will be exposed and the protective coating must not be damaged.

TREATMENT OF 247 CASES OF PROLAPSE OF LUMBAR INTERVERTEBRAL DISC WITH COMPREHENSIVE PLUM-BLOSSOM MAGNETIC NEEDLE THERAPY

Objective: To observe the therapeutic effect of comprehensive plum-blossom magnetic needle therapy on prolapse of lumbar intervertebral disc. Methods: 247 cases of prolapse of lumbar intervertebral disc were treated first with manual treatment and then with plum-blossom magnetic needle therapy and effect-increasing pad therapy at specified points and reactive points. Results: After treatment for 2 therapeutic courses,153 cases were cured accounting for 61.94%, 71 cases were markedly effective accounting for 28.75%, 22 cases were improved accounting for 8.91% and the rest one failed,accounting for 0.45%. Conclusion: The comprehensive plum-blossom magnetic needle therapy has a better therapeutic effect on prolapse of lumbar intervertebral disc.

3D Magnetic Field Computation of a Permanent MagnetDisc-Type Generator Using Scalar Potential Method

The three-dimensional magnetic field of a permanent permanent (PM) disc-type generator is analyzed by the scalar potential method. In the analysis the permanent magnets are taken as magnetic charges. Hexahedron element meshes are automatically generated by a prc-proccssing program developed by the authors. The flux densily is computed by a 3D scalar potential method program. Based on the linite elcment analysis the induced emf, current, armaturc reaction effects and electromagnetic torque of the disc machine are all calculated.

颞下颌关节紊乱病的MRI临床应用进展

随着颞下颌关节影像检查手段的发展,磁共振成像逐渐成为颞下颌关节紊乱病的首选检查方法,由于其无电离辐射暴露风险且为非侵入性检查,可清晰显示关节盘、关节腔积液、髁突水肿、咀嚼肌、双板区及滑膜病变,在临床有较大应用价值。本文从关节盘位置及形态改变、关节腔积液、髁突水肿和翼外肌的磁共振成像表现及其相关性研究现状进行探讨,以期为颞下颌关节紊乱病影像诊断提供思路。

颞下颌关节盘前移位患者盘-髁复合体MRI特征及盘周附着半量化评级研究

目的通过盘-髁复合体磁共振成像(magnetic resonance imaging,MRI)特征分析及盘周附着半量化评级法,探讨颞下颌关节可复性盘前移位(anterior disc displacement with reduction,ADDWR)与不可复性盘前移位(anterior disc displacement without reduction,ADDWoR)中关节盘形态、髁突形态及盘周附着处之间的相关性。材料与方法回顾性分析2021年5月至2022年9月于福建省级机关医院行MRI检查确诊为颞下颌关节盘前移位74例患者共114侧,分为ADDWR组39侧和ADDWoR组75侧,比较关节盘形态Ⅰ~Ⅳ类型、髁突形态3类别及盘周附着处半量化评分分级6级。采用Kruskal-Wallis检验比较两组中不同关节盘形态类型、髁突形态类别及盘周附着分级之间差异。采用Mann-Whitney U检验比较两组之间关节盘形态、髁突形态、盘周附着处总评分及各处附着评分差异。采用Spearman秩相关分析关节盘形态、髁突形态、盘周附着处总评分及各附着与盘-髁复合体可复性与否的相关系数。采用二元logistic回归方法对盘周附着的模型筛选出独立危险因素,作为盘-髁复合体是否可复性的预测。结果除Ⅲ型与Ⅳ型外,两组关节盘形态类型差异均有统计学意义(P<0.05)。两组髁突形态类别差异均有统计学意义(P<0.05)。除1级至4级、5级/6级外,两组盘周附着评分分级差异均有统计学意义(P<0.05)。关节盘可复性与否和关节盘形态、髁突形态及盘周附着处总评分存在较强的正相关性(r分别为0.824,0.626及0.827,P<0.05)。盘周附着处的logistic回归预测模型筛选发现下板附着处是关节盘可复性与否的独立危险因素,回归系数为2.979(OR=19.672,P<0.05)。结论基于盘-髁复合体MRI征象分析及半量化评级法,能有效地评估关节盘可复性与否的相关性因素,为临床治疗提供可靠的影像学参考。

冠状位磁共振成像PROSET水激发序列对多节段腰椎间盘突出症致病节段的诊断价值

目的评估冠状位磁共振成像和PROSET水激发序列对多节段腰椎间盘突出症致病节段的准确性。方法回顾性分析2019年1月至2022年12月在我院接受手术治疗的66例多节段腰椎间盘突出症患者临床和影像学资料。MRI检查使用3.0TMR扫描仪(荷兰Philips Ingenia公司,3.0T),之后使用冠状位PROSET水激发序列进行扫描。收集MRI图像上多节段腰椎间盘突出症的表现及与神经根受压关系。以术中和术后患者疗效为受压神经根节段的判断标准,分析计算冠状位MRI诊断受压神经根的敏感性、特异性、阳性预测值、阴性预测值和准确性。并使用Kappa一致性分析两者诊断一致性。结果66例多节段腰椎间盘突出症患者,MRI图像上共识别到31例患者存在2节段腰椎间盘受累,25例存在3节段受累,10例存在4节段受累,共涉及177个椎间盘。在冠状位腰椎MRI上,椎间盘突出症引起的神经根压迫存在一系列形态学变化,包括神经根凹陷、神经节信号增强、神经根肿胀或神经根断裂。L4/L5神经根起点多位于椎间盘平面(69.81%),L5/S1神经根起点多位于椎间盘上方(72.58%)。共79处神经根受压,其中以L5的神经根受压比例最高82.28%(65/79)。冠状位MRI在多节段椎间盘突出症患者定位致病节段的诊断敏感性为97.4%、特异性为99.3%、阳性预测值为93.7%、阴性预测值为98.6%、准确性为98.6%。冠状位MRI与术中及术后诊断Kappa一致性高(k=0.926)。结论冠状位MRI对定位多节段椎间盘突出症患者的致病节段、受压神经根具有较高准确性,值得今后进一步研究。

郑氏中医康复综合疗法治疗腰椎间盘突出症患者的疗效评价

目的 评估郑氏中医康复综合疗法与常规保守治疗腰椎间盘突出患者的临床疗效。方法 收集我院腰椎间盘突出症患者共60例。采用随机数字法将患者分为试验组及对照组各30例,对照组采用常规保守治疗,试验组在此基础上给予郑氏中医康复综合治疗。比较两组患者治疗有效率,治疗前、后的腰椎间盘突出率、疼痛VAS评分及下腰功能JOA评分。结果 试验组治疗总有效率高于对照组(96.67%vs 76.67%,P<0.05)。治疗后,两组VAS评分均较治疗前降低,JOA评分均较治疗前升高,且试验组优于对照组(P<0.05);治疗后,试验组腰椎间盘突出率较前有减少,且低于对照组(P<0.05)。结论 郑氏中医康复综合治疗能改善腰椎间盘突出症患者的临床症状,有利于突出椎间盘组织的回纳及吸收。