Dependence of Effective Anisotropy on Grain Size in Nanocrystalline Nd2 Fe14 B Hard Magnetic Material

Anisotropy of material is the key factor determin ing coercivity and anisotropy of nano grain is dramati cally influenced by grain size[1~2]. So the coercivityof nano magnetic material with different grain sizeswould have obvious difference.…     

Anisotropy of rare-earth magnets

Rare-earth intermetallics such as Nd₂Fe₁₄B and Sm-Co are widely used as high-performance permanent magnets, because they combine high magnetocrystalline anisotropy with reasonable magnetization and Curie temperature. The anisotropy is a combined effect of spin-orbit coupling and electrostatic crystal-field interactions. The main contribution comes from the rare-earth 4f electrons, which are well-screened from the crystalline environment but exhibit a strong spin-orbit coupling. In this limit, the magnetocrystalline anisotropy has a very transparent physical interpretation, the anisotropy energy essentially being equal to the energy of Hund's-rules 4f ion in the crystal field. The corresponding expression for the lowest-order uniaxial anisotropy constant K₁ is used to discuss rare-earth substitutions, which have recently attracted renewed interest due to shifts in the rare-earth production and demand. Specific phenomena reviewed in this article are the enhancement of the anisotropy of Sm₂Fe₁₇ due to interstitial nitrogen, the use of Sm-Co magnets for high-temperature applications, and the comparison of rare-earth single-ion anisotropy with other single-ion and two-ion mechanisms.     

Effect of Rare Earth Cerium on Yield Strength Anisotropy of Al-Li Alloy Sheet and Its Theoretical Prediction

Traceadditionofrareearthinto 2 0 90Al Lialloyisoneofthemeasurestoimproveitslowductilityandtoughness .Al Lialloysheetwithstrongcrystallo graphictexturehasbeenknowntohaveunusuallyhigheryieldstrengthanisotropythanconventionalalu minumalloys[1～3] .However ,ithasnotbeennormallyrecognizedsofarabouttheeffectofceriumonthisanisotropyofAl Lialloy .Someinvestigationsonheat treatableAl Lialloysshowthattheyieldstrengthanisotropyof 2 0 90sheetalloyisdefinitelyassociatedwiththevolumefractionofT1precipita…     

Electronic Theoretical Study of the Interaction between Rare Earth Elements and Impurities at Grain Boundaries in Steel

Rareearths(RE)aresurfaceactiveelements ,theirapplicationsinmetalmaterialscanbesum marizedaspurification ,modificationandall oying[1～ 3 ] .Itisaveryattractivesubjectthattheinter actionofREelementswithlowmeltingpointimpuri tiesintheregionofGBs ,suchasP ,S ,As ,Sbandsoon .ResultsofexperimentsshowthatsegregationinGBsofasmallamountofREinsteelrestrainsharmfulimpuritiessuchasP ,S ,As ,Pb ,Sb ,tosegregateto wardsGBs ,soREelementscancleanseandenhanceGBs ,therebyimprovethehightemperatureducti…     

RE_2(CoFe)_(17-x)Ti_x型合金的结构和磁性(RE=Nd,La)

用电子探针 (EPMA)、X射线衍射仪和 2 0T脉冲强磁场测试仪研究了RE2 (CoFe) 1 7-xTix(RE =Nd ,La)的结构与磁性。结果表明 ,Nd2 Co1 7-xTix经过 10 5 0℃× 15h均匀化处理 ,在x =1时 ,Nd2 Co1 7型化合物变成Nd(CoTi) 1 2 和Nd2 (CoTi) 7型化合物 ,而呈现出单轴各向异性。此时合金的饱和磁化强度为 0 .7T ,各向异性场为 2 2 5 0 .3kA·m- 1 。对La Co Fe Ti2∶17型合金的磁特性进行了研究。随着铁含量的增加 ,合金的饱和磁化强度明显增加 ,但也明显地降低了各向异性场     

Thermodynamic Assessment of Interaction Relation between Lanthanum and Constituent Elements in Sn-Pb Alloy

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Dependence of Magnetic Properties of Rapidly Quenching （Nd, Pr）x（FeCoZr）94-xB6 Bonded Magnets on Rare Earths Content

By using sub-everquenching and annealing method which has a wide processing window, (Nd, Pr)x(Fe-CoZr)94-xB6(x=12, 10.5, 10, 9) bonded magnets were prepared and the effect of rare earths content on magnetic properties was investigated. Being spun at sub-ove, quenching speed the as-spun ribbons consist of amorphous phases mixed with fine crystallites. After crystallization under optimum annealing conditions and bonded with 3.25%(mass fraction) epoxy, the magnets obtained the optimum magnetic properties. The rare earths content directly determines the magnetic properties. With the reduction of rare earths content, Br increases but Hci and (BH)max decrease, x=10 is the critical value for the magnetic properties change. Below this value, Br increases slowly meanwhile Hci and (BH)max decrease strongly because alloy contains extra fractions of soft magnetic phase which are not coupled with the hard magnetic phase. This experimental result is consistont with the calculated results using the model of volume fraction of soft magnetic phase coupled completely suggested.     

Review of Rare Earths and Fluid-Rock Interaction

As demonstrated by a great amount of geologic and experimental evidences, RE of rock systems may be mobilized during fluid-rock interaction when solutions are rich in F^-, Cl^-, CO3^2- , HCO3^-, CO2, HPO4^2- , HS^-,S^2- , SO4^2- , though little has been known about the mobilizing mechanism of these anions or ligands. The fractionation of RE resulted from hydrothermal alterations, i. e., fluid-rock interactions, are distinctive. One set of field data implies the preferential mobility of the LRE, while another set of field observations demonstrates the dominant mobilization of the HRE, and some theoretical prediction is not consistent with the field evidence. The Eu anomalies caused by fluid-rock interaction are complex and compelling explanation is not available due to inadequate experimental approaches. To know the exact behavior of RE during fluid-rock interaction and to solve the contradiction between some theoretical predictions and field observations, the following works remain to be done : ( 1 ) experimental investigations of RE mobility and fractionation as a function of fluid chemistry, e.g., the activity of F^-,Cl^-, CO3^2- , HCO3^-, CO2, HPO4^2- , HS^-, S^2- , SO4^2- , etc. ; (2) experimental determination of RE mobility and fractionation as a function of T, P, pH, Eh and water/rock ratios; (3) investigation of the mechanism and the controlling factors of RE partitioning between hydrothermal minerals and fluids. It was demonstrated that RE mobility is a potentially useful method for exploration.     

Behaviors of Rare Earths during Fluid-Rock Interaction and Its Significance of Geochemistry

Ｒａｒｅｅａｒｔｈｓ (ＲＥ)ａｒｅｐｏｗｅｒｆｕｌｔｒａｃｅｒｓｉｎｔｈｅｓｔｕｄｙｏｆｅｖｏｌｕｔｉｏｎｏｆｇｅｏｃｈｅｍｉｃａｌｓｙｓｔｅｍｓ .Ｔｈｅｙｈａｖｅｂｅｅｎｕｓｅｄｏｖｅｒｔｈｅｐａｓｔ 3 0ｙｅａｒｓａｓａｔｏｏｌｆｏｒｓｏｌｖｉｎｇｖａｒｉｏｕｓｇｅｏｌｏｇｉｃａｌｐｒｏｂｌｅｍｓ .ＴｈｅａｐｐｌｉｃａｔｉｏｎｏｆＲＥａｂｕｎｄａｎｃｅｓｔｏｐｅｔｒｏｇｅ ｎｅｔｉｃｐｒｏｂｌｅｍｓｈａｓｃｅｎｔｅｒｅｄｓｏｆａｒｏｎｔｈｅｅｖｏ ｌｕｔｉｏｎｏｆｉｇｎｅｏｕｓｒｏｃｋｓ ,ｗｈｅ…     

Magnetic Properties of （Sm, Tb）FeCo/Cr/TbFeCo Trilayers with Perpendicular Anisotropy

A series of （Sm, Tb）FeCo/Cr/TbFeCo trilayers with perpendicular anisotropy was prepared by RF magnetron sputtering, and the effect of Cr interlayer thickness on magnetic properties and interlayer exchange coupling was investigated. All the samples showed strong out-of-plane anisotropy but their hysteresis loops displayed two types ： singlephase and double-phase, indicating that interlayer exchange coupling and magnetic properties varied with the thickness of Cr interlayer. Both saturation field Hs and （1-Mr/Ms） curves indicated that interlayer exchange coupling oscillated between antiferromagnetic and ferromagnetic with a period of 1.6 nm, and the oscillation strength attenuated with increasing Cr interlayer thickness. After being annealed at 450℃ for 25 min, the hysteresis loops of all the samples became single-phase type and coercivity Hc decreased greatly, which could be attributed to the decrease of effective anisotropy in （Sm, TbFeCo） grains.     

Y2(Co,Si)17化合物的结构与磁晶各向异性

采用真空电弧熔炼法制备了 Y2 Co17- x Six化合物。用 X-射线衍射和磁性测量方法 ,研究了化合物的晶体结构和内禀磁性。实验结果表明 ,随 Si原子浓度增加 ,Y2 Co17- x Six化合物的居里温度和饱和磁化强度急剧下降。本文重点讨论了 Si原子在 Co次晶格的四个不同晶位择优占位与 Co次晶格磁晶各向异性从易面转变为易轴的演化关系 ,其中 1 8h晶位对 Co次晶格各向异性负贡献起重要作用。     

Effect of Zirconium Content on Microstructure and Magnetic Properties of Nanocomposite Bonded Magnets

Five kinds of bonded magnets with compositions of Nd10.5Fe78.4-xCo5ZrxB6.1(atom percentage x＝0,1.0,1.5,2.0,2.5)were prepared by rapid quenching, post heat treatment and mould-pressing.The microstructure and crystallization behavior were studied by X-ray diffraction (XRD), differential thermal analysis (DTA) and atomic force microscopy (AFM). The results suggest that high content of Zr can increase the glass formation ability (GFA) of alloys. When the content of Zr is controlled at a certain level, Fe2Zr with high melting point is formed in the alloys, and grain size is reduced consequently. At the same time, because of Zr addition, the coercivity and squareness of demagnetization loop are obviously improved, and the energy product is accordingly increased. As a result, optimal magnetic properties of Nd10.5Fe78.4-xCo5ZrxB6.1(Br＝0.659 T,Hcj＝628 kA·m-1,Hcb＝419 kA·m-1,(BH)m=73 kJ·m-3) are obtained when x=2.     

Anisotropic Magnetoresistance of Perovskite La_(2/3)Ca_(1/3)MnO_3/YBa_2Cu_4O_8/La_(2/3)Ca_(1/3)MnO_3 Trilayer Films

Magneticanisotropyhasbeenfoundinmanyex oticmaterials,suchasmetallicsuperlatticeswithgi antmagnetoresistanceeffectsandthehightempera turesuperconductingoxideYBa2Cu3O7 δ[1～4].The anisotropycouldfindnovelusesinnewdeviceappli cations.Agoodexampleisthehig…     

稀土永磁及磁记录材料的矫顽力与有效激活体积

指出了文献 [1]中的一个错误。给出了不同模型的稀土永磁材料以及磁记录材料的矫顽力 Hc和有效激活体积υ之间的正确关系 ,这样的关系被表示成一个复杂的函数关系 ,同时指出 ,对不同模型的稀土磁性材料 ,这个函数关系是不同的     

在La_(0.67)Sr_(0.33)MnO_3中保持Mn~(3+)∶Mn~(4+)=2∶1的镁掺杂效应

通过测量样品的M T曲线、M H曲线、ESR曲线、红外光谱、拉曼光谱、ρ -T曲线和MR T曲线 ,研究了双掺杂La0 .6 7+ 1 .33xSr0 .33- 1 .33xMn1 -xMgxO3(0.0 0≤x≤ 0 .2 5 )体系的磁电性质和输运行为。对x =0 .10和 0 .15 ,在温度高于TConset时出现相分离 ;对x =0 .2 0和 0 .2 5 ,在低温区出现了反铁磁 (AFM )行为。x =0 .0 5的 ρ-T关系存在金属 绝缘体 (MI)转变 ;x≥ 0 .15的所有样品在测量温区内显示绝缘体行为。这些奇异现象用M H关系、ESR曲线和拉曼光谱给予了很好的解释     

稀土草酸盐的溶解度与稀土氧化物粒度之间的关系及粒度控制

通过稀土草酸盐溶液度与粒度的关系。探索控制稀土氧化物粒度的途径。实验测定了几种稀土草酸盐在草酸沉淀母液中的溶解度，并对不同草酸沉淀条件下获得的单一稀土氧化物的粒度进行比较。得到了其氧化物粒度与草酸盐溶解度之间的关系，通过对Y2O3，Eu2O3,Gd2O3,Dy2O3的粒度数据进行分析对照，提出了控制其粒度的途径。     

Structure and Magnetocaloric Effect in Tb（ Co1-xSnx）2 Alloys

Recently,researchonmagnetocaloriceffect(MCE)hasattractedagreatdealofinterestinrare earth(RE)basedcompoundsbecauseoftheirenergy efficiencyandenvironmentalsafetyformagneticrefrig eration.Afirst ordermagneticphasetransitionwas foundintheintermetalliccompoundsRECo2(RE=Er,Ho,Dy)withMgCu2typestructure[1,2],leadingtoa largemagneticentropychangeforthesecompounds,whereasasecond ordertransitionwasfoundinTbCo2andGdCo2.IntheintermetalliccompoundsRECo2,theloweringofd electronconcentrationbythesubst…     

Structure and magnetic properties of new compounds CdYFeWO_7

The solid solutions of CdYFeWO7,which are cubic pyrochlores of the type A2B2O7,have been prepared and their structures were determined using Ab initio method.Rietveld refinement of the powder XRD data showed that CdYFeWO7 adopted cubic(Fd-3m) structure,while oxides crystallized in a defect-pyrochlore structure where both O(48f) and O'(8b) sites were partially occupied,and the frustrated cations sublattice precluded long range ordering of Fe/W in the pyrochlore structure.Charge distribution analysis also sug...     

Mechanism of Action of Rare Earths in High Effective Fe Powder Welding Rods

The optimum coating composition of alkali Fe powder welding rods was designed by orthogonal experiment with mix rates. A new kind of effective RE-Fe powder welding rod was prepared which could be used at the condition of direct and indirect current. The arc characteristics and stabilities of effective Fe powder welding rods containing RE were analyzed by HANNOVER analyzer. The efficiency of Fe powder welding rods was tested by weighting method. It wag found that the stability of Fe powder welding rods Wag improved when it was added with rare earths. The results of impact experiment at low temperatures and SEM analysis on impact break showed that the grain was refined, the welding joint was cleaned, and the mechanical properties of joint was enhanced with proper RE content. It was provided with good processing property for this effective RE-Fe powder welding rod, and its efficiency could arrive at 180%.     

Effects of Light and Heavy Rare Earths on Anti-Degradation of Nodular Cast Iron

The effects of rare earths with different contents on anti-degradation of Y base heavy rare earths-magnesium and cerium base light rare earths-magnesium nodular cast iron were studied. Curves of the relationship between the spheroidization grade of liguid iron treated by different nodulizers and holding time were obtained. The results show that the more the remains of the rare earth, the longer the anti-degradation time, the liquid iron was treated either by Y-Mg-Si or by Ce-Mg-Si nodulizer. When the rare earth remains are above certain quantity, the spheroidization grade starts to decline. When liquid iron treated by either Y-Mg-Si or Ce-Mg-Si nodulizer with proper remains of rare earths about 0.04% 0.06%（mass fraction）, the anti-degradation is the best, and the remains of Mg being about 0.04% -0.07% （mass fraction）. Rare earths-Mg nodulizer with moderate RE remains is better than that of Mg-Si nodulizer in anti-degradation property. However, Y-Mg-Si nodulizer with moderate remins of Re is better than Ce-Mg-Si nodulizer. Sometimes Ce-Mg- Si nodulizer can be used for the production of heavy section nodular cast iron.