共查询到20条相似文献,搜索用时 15 毫秒
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Changes in the magnetic field-temperature phase diagram of CeSb with pressure have been determined up to 6kbar by magnetization measurements on a single crystal. High magnetic fields up to 70 kOe have been applied along a four fold axis of the rock-salt type structure. The features of the phase diagram are not changed by pressure except for a shift towards high temperature. The saturated magnetic moment and the hysteresis of the transition fields are independent of pressure. Variation of exchange energy with volume is deduced from the experimental results. It is shown that the effect of pressure and the magnetic volume anomaly at 0 K are essentially due to the variation of the exchange energy in the ferromagnetic (001) planes. 相似文献
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《Journal of magnetism and magnetic materials》1987,68(3):331-334
The results of magnetic measurements performed on Nd2Fe12−xSixCo2B alloys with 0⩽x⩽0.6 are presented. All the compound studied crystallize in the tetragonal Nd2Fe14B structure. The unit cell volume is found to decrease by introducing Si. With substitution of Fe by Si, the saturation moments decrease, but theanisotropy fields and Curie temperatures are found to increase significantly. For example, in Nd2Fe11.5Si0.5Co2b, at room temperature, μs=28.4μB, HA=80 kOe and Tc=736 K. 相似文献
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The spin echo NMR spectra of59Co for GdCo2Si2 are reported. A weak negative hyperfine field on Co nuclei was found in magnetically ordered state of the compound. The splitting
of resonance lines in external magnetic field indicates on antiferromagnetic structure of Gd moments lying in thea-a plane with energetic minima in [100] and [110] directions as in GdFe2Si2 and GdNi2Si2. 相似文献
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G. Wiesinger R. Grössinger R. Krewenka X. C. Chou X. K. Sun Y. C. Chuang 《Hyperfine Interactions》1989,50(1-4):693-699
Various efforts are currently undertaken to raise the relatively low Curie temperature of the otherwise promising Nd?Fe?B type permanent magnet material. The substitution of Fe by several elements was found to increaseT c, which, on the other hand, can be accompanied by a reduction of the magnetocrystalline anistropy. In the present paper a systematic Mössbauer study was carried out, using Co, Ni, Al, Si and Ga as substituents. The specific influence of each element upon the magnetic properties is attributed to its preference for entering a certain Fe lattice site. Simple atomic size considerations are proved to be insufficient for explaining the preferred occupation observed experimentally. Obviously the local electronic structure has to be studied more carefully. Finally, the interplay between magnetism and metallurgy (particularly the formation of precipitations), is found to be of some importance. 相似文献
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Z. Arnold O. Isnard H. Mayot Y. Skorokhod J. Kamarád M. Míšek 《Solid State Communications》2012,152(13):1164-1167
The effects of hydrostatic pressure up to 10 kbar on Curie temperature TC, compensation temperature TCOMP and spontaneous magnetization MS of ferrimagnetic GdCo12B6 compound have been studied. Two antiferromagnetically coupled sublattices that are carrying magnetization of typically 0.42 μB/Co atom and 7 μB/Gd cancel out at compensation temperature at about 50 K and magnetic ordering temperature TC=163±2 K. The volume dependence of intrinsic magnetic properties of the GdCo12B6 compound has been determined by studying it under hydrostatic pressure. The observed increase of MS with pressure (dMS/dp=+0.005 μB kbar?1 at 5 K) is attributed predominantly to the pressure induced decrease of Co magnetic moments. The crucial role of Co in this behavior is confirmed by the change of sign of the pressure slope at temperatures above TCOMP and by the fact that the estimated decrease of mCo is also quite comparable with pressure induced decrease of MS in YCo12B6 (dMS/dp=?0.007 μB kbar?1). The decrease of mCo is also responsible for the increase of TCOMP with pressure (dTCOMP/dp=+0.06 K kbar?1). The decrease of TC with pressure (dTC/dp=?0.55 K kbar?1) is comparable to the decrease observed on RCo12B6 compounds with non-magnetic R and can be attributed to the volume dependence of Co–Co exchange interactions. The remarkable role of the hybridization as a consequence of small distances between Co and B atoms could be a background of this rather unexpected volume stability of magnetic properties. 相似文献
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采用熔体快淬的方法制备Pr2Fe14B/α-Fe纳米晶复合永磁材料.使用振动样品磁强计(VSM)测量样品的室温磁性能.实验合金成分为(PrxFe94.3-xB5.7)0.99Zr1(其中x=8.2,8.6,9.0,9.4,9.8,10.2,10.6,11.0,11.4(原子分数,%)).系统地研究了辊速及合金成分对快淬带磁性能的影响,当Pr原子分数由8.2%-11.4%变化时,矫顽力Hci升高,但剩余磁极化强度Jr却降低了,这是导致最大磁能积(BH)max下降的原因.当x=8.2(%)时,尽管样品的Hci较低,但高的Jr使(BH)max的值达到很高,在辊速为25m/s时得到最佳磁性能为:Jr=1.37T,Hci=501.19kA/m,(BH)max=227.93kJ/m3.同时发现垂直带面方向的Jr和(BH)max远高于平行带面方向. 相似文献
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采用快淬方法制备了纳米晶复合Pr2Fe14B/α-Fe永磁薄带,研究了不同淬火速率对薄带织构和磁性的影响.通过改善快淬工艺,使得薄带中Pr2Fe14B相的晶粒在薄带的自由面形成显著的织构,Pr2Fe14B相晶粒易轴沿垂直于带面方向取向.分析了快淬凝固过程中Pr2Fe14B相的晶粒取向过程和机理,以及晶粒的大小和薄带结构的均匀性对薄带磁性的影响.对自由面有显著取向的薄带,进行酸蚀和打磨减薄处理,去除贴辊面未取向的部分,剩余部分为具有Pr2Fe14B相晶粒取向的各向异性薄带,Pr2Fe14B相取向使薄带的剩磁得到增强,矫顽力也有所提高.
关键词:
快淬
2Fe14B/α-Fe永磁薄带')" href="#">纳米晶复合Pr2Fe14B/α-Fe永磁薄带
织构
磁性能 相似文献
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Z. Arnold O. Isnard H. Mayot M. Mí?ek J. Kamarád 《Journal of magnetism and magnetic materials》2010,322(9-12):1117-1119
The effect of pressure on magnetic properties of YCo12B6 and CeCo12B6 was studied in temperature range 5–300 K at pressures up to 9 kbar. The Curie temperature TC and spontaneous magnetization MS decrease with pressure for both compounds. The decrease can be attributed mostly to the volume dependence of both, the Co magnetic moment and the exchange interactions. The hybridization of the p–d states as a consequence of small distances between the Co and B atoms can be one reason of the relatively low pressure effects (ΔTC/Δp=?0.39±0.02 K/kbar, d ln MS/dp=?0.0013±0.0002 kbar?1) in YCo12B6. Higher volume sensitivity of magnetic properties of CeCo12B6 in comparison with YCo12B6 can be attributed to the pressure induced changes of the Ce f- and Co d-states. 相似文献
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基于密度泛函理论的第一性原理方法,系统研究了0~30 GPa压力下四方相Fe2B的结构,稳定性和力学性质等.随着压力的增加,计算得到的晶格参数逐渐减小,所有结构均满足热力学稳定性,体积模量和剪切模量逐渐增大,韧性得到有效改善.硬度呈现先增大后减小的趋势,并在18 GPa压力时达到最大值,各向异性先增大后减小.德拜温度变化趋势与杨氏模量的变化趋势相同.同时还研究了相变结构——正交相的相关性质,结果表明其结构满足热力学稳定性但不满足力学稳定性,是否稳定存在还需要进行后续实验研究. 相似文献
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Haibo Xiao Ruilong Wang Linfang Xu Fujun Yang Changping Yang 《Physics letters. A》2018,382(4):224-230
First-principles calculations are performed to investigate pressure effects on structure, magnetism, martensitic phase transition and Curie temperatures of Mn2PtGa Heusler alloy in framework of the density functional theory. It is shown that Mn2PtGa prefer to crystallize in the inverse Heusler type structure. Besides, we predict an extraordinary occurrence of pressure induced metallic ferrimagnetism to half-metallic ferromagnetism transition in cubic phase of Mn2PtGa alloy under hydrostatic pressure up to 43 GPa and the half-metallic ferromagnetism is found to be robust even the lattice further compression to 90 GPa. However, with the pressure up to 100 GPa, the spin-down gap starts to close and the half metallicity begin to disappear, while with the pressure increasing from 100 GPa to 300 GPa, the alloy returns to metallic characteristic. In addition, the energy difference between the austenitic and martensitic phases is found to increase with increasing pressure followed by a decrease when pressure reaches to 43 GPa, which implies a variation trend of martensitic phase transition temperature. Furthermore, Curie temperatures in both austenitic and martensitic phases are estimated under pressure by using the standard mean-field approximation which agrees well with the theoretical results in literature. The robustness of the half metallicity, magnetic transition and the high Curie temperature under pressure make Mn2PtGa alloy a promising candidate for applications in spintronic devices. 相似文献
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《Journal of magnetism and magnetic materials》2001,224(1):5-11
The magnetic properties of Fe2O3 nanoparticles (average diameter ∅≅3 nm) in alumina (68% Fe2O3 in weight) have been investigated by magnetization measurements. The results indicate a superparamagnetic behavior of interacting particles, which block with decreasing temperature (the zero-field-cooled susceptibility shows a maximum at T≅145 K) with a distribution of relaxation times. A change of magnetic regime is observed below ∼60 K, due to the increasing interparticle interactions and local surface anisotropy. 相似文献
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《Journal of magnetism and magnetic materials》1990,92(1):L35-L38
We have shown that ternary rare earth nitrides of the approximate composition R2Fe17N2.5 can be prepared by the reaction of R2Fe17 with nitrogen gas at 500°C for all members of this series. The crystal structure and lattice constants of these compounds have been determined and are discussed in terms of volume increase and nitrogen site occupation. The N2 uptake was found to be accompanied by strong increases of the Curie temperature and room temperature magnetization. From the results it was derived that the N2 uptake may lead to substantial changes in the RFe coupling strength. 相似文献
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We systematically investigate the effect of pressure on the magnetic properties of GdCo_2B_2 on the basis of alternating current(AC) susceptibility,AC heat capacity and electrical resistivity measurements under pressures up to 2.2 GPa.A detailed magnetic phase diagram under pressure is determined.GdCo_2B_2 exhibits three anomalies that apparently reflect magnetic phase transitions,respectively,at temperatures T_C= 20.5 K,T_1= 18.0 K and T_N= 11.5 K under ambient pressure.Under pressures up to 2.2 GPa,these anomalies are observed to slightly increase at T_Cand T_1,and they coincide with each other above 1.6 GPa.Conversely,they decrease at T_N and disappear under pressures higher than 1.4 GPa.The results indicate that the low-temperature magnetic phases can be easily suppressed by pressure.Moreover,the spin-glass-like behavior of GdCo_2B_2 is examined in terms of magnetization,aging effect and frequency dependence of AC susceptibility.A separation between the zero-field-cooled(ZFC) and field-cooled(FC) magnetization curves becomes evident at a low magnetic field of 0.001 T.A long-time relaxation behavior is observed at 4 K.The freezing temperature Tfincreases with frequency increasing. 相似文献
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《Journal of magnetism and magnetic materials》2005,294(2):e155-e158
The evolution of the magnetic properties of Fe70Cr10B20 alloy, initially in amorphous state, is studied during the whole crystallization process, from room temperature to 800 °C. Neutron thermodiffraction has been used in order to follow all the structural changes that take place in the sample, including the appearance of tetragonal phases and polymorphic transformations. The formation of these tetragonal phases, with high magnetic anisotropy, leads to a degradation of the soft magnetic response. The study of the correlation between structure and magnetic response helps to optimize the composition and heat treatments in these materials for their application in sensor devices. 相似文献
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E. A. Tereshina I. S. Tereshina S. A. Nikitin G. S. Burkhanov O. D. Chistyakov I. V. Telegina V. A. Belousova T. Palewski H. Drulis 《Physics of the Solid State》2008,50(1):56-62
Hydrogenated single crystals Er2Fe14Bh x with different hydrogen contents are grown and their magnetic properties are studied for the first time. It is established that both the Curie temperature and the temperature of the spin-reorientation phase transition increase with an increase in the hydrogen content. In the Er2Fe14B single crystal, the contributions of the rare-earth metal and iron sublattices to the magnetic anisotropy decrease upon hydrogenation. However, their compensation occurs at a temperature higher than that in the initial compound Er2Fe14B due to the enhancement of the Fe-Fe and R-Fe exchange interactions. The effect of hydrogenation on the magnetic characteristics of the Er2Fe14B compound with a nanocrystalline structure is investigated. It is revealed that the hydrogenation leads to an increase in the coercive force and the residual magnetization of these alloys. 相似文献