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Rare Metals 2007年第2期26卷 176-181页

作者： WU Ping GAO Yanqing QIU Hong PAN Liqing TIAN Yue Wang Fengping Department of Physics University of Science and Technology Beijing Beijing 100083 China

Ni80Fe20/Ni48Fe12Cr40 bilayer films and Ni80Fe20 monolayer films were deposited at room temperature on SiO2/Si（100） substrates by electron beam evaporation. The influence of the thickness of the Ni48Fe12Cr40 underlayer on the structure, magnetization, and magnetoresistance of the Ni80Fe20/Ni48Fe12Cr40 bilayer film was investigated. The thickness of the Ni48Fe12Cr40 layer varied from about 1 nm to 18 nm while the Ni80Fe20 layer thickness was fixed at 45 nm. For the as-deposited bilayer films the introducing of the Ni48Fe12Cr40 underlayer promotes both the （111） texture and grain growth in the Ni80Fe20 layer. The Ni48Fe12Cr40 underlayer has no significant influence on the magnetic moment of the Ni80Fe20/Ni48Fe12Cr40 bilayer film. However, the coercivity of the bilayer film changes with the thickness of the Ni48Fe12Cr40 undedayer. The optimum thickness of the Ni48Fe12Cr40 underlayer for improving the anisotropic magnetoresistance effect of the Ni80Fe20/Ni48Fe12Cr40 bilayer film is about 5 nm. With a decrease in temperature from 300 K to 81 K, the anisotropic magnetoresistance ratio of the Ni80Fe20 （45 nm）/Ni48Fe12Cr40 （5 nm） bilayer film increases linearly from 2.1% to 4.8% compared with that of the Ni80Fe20 monolayer film from 1.7% to 4.0%.

关键词： Ni80Fe20 films Ni48Fe12Cr4o seed layer structure magnetic properties

magnetic properties of Sn-substituted Ni-Zn ferrites synthesized from nano-sized powders of NiO, ZnO, Fe2O3, and SnO2

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Chinese Physics B 2017年第7期26卷 377-382页

作者： M A Ali M M Uddin M N I Khan F U Z Chowdhury S M Hoque S I Liba Department of Physics Chittagong University of Engineering and Technology (CUET) Materials Science Division Atomic Energy Center

A series of Ni0.6-x/2Zn0.4-x/2SnxFe2O4(x = 0.0, 0.05, 0.1, 0.15, 0.2, and 0.3)(NZSFO) ferrite composities have been synthesized from nano powders using a standard solid state reaction technique. The spinel cubic structure of the investigated samples has been confirmed by x-ray diffraction(XRD). The magnetic properties such as saturation magnetization(Ms),remanent magnetization(Mr), coercive field(Hc), and Bohr magneton(μ) are calculated from the hysteresis loops. The value of Msis found to decrease with increasing Sn content in the samples. This change is successfully explained by the variation of A-B interaction strength due to Sn substitution in different sites. The compositional stability and quality of the prepared ferrite composites have also been endorsed by the fairly constant initial permeability(μ’) over a wide range of frequency. The decreasing trend of μ’ with increasing Sn content has been observed. Curie temperature TChas been found to increase with the increase in Sn content. A wide spread frequency utility zone indicates that the NZSFO can be considered as a good candidate for use in broadband pulse transformers and wide band read-write heads for video recording. The composition of x = 0.05 shows unusual results and the possible reason is also mentioned with the established formalism.

关键词： magnetic properties saturation magnetization permeability Curie temperature

magnetic properties and microstructures of terbium coated and grain boundary diffusion treated sintered Nd-Fe-B magnets by magnetron sputtering

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Journal of Rare Earths 2021年第2期39卷 167-173页

作者： Wei Zhu Yang Luo Zilong Wang Xinyuan Bai Haijun Peng Dunbo Yu National Engineering Research Center for Rare Earth Materials GRINM Group Co.Ltd.Beijing 100088China GRIREM Advanced Materials Co. Ltd.Beijing 100088China General Research Institute for Nonferrous Metals Beijing 100088China

Tb coating on the surface of commercial sintered Nd-Fe-B magnet was prepared by DC magnetron *** secondary heat treatment was used to regulate the microstructure for the enhancement of coercivity,namely diffusion treatment and annealing *** coercivity increases significantly from 18.3 to 28.0 kOe,the remanence decreases slightly from 14.1 to 14.0 kGs,and the comprehensive magnetic properties are higher than 75(Hcj+(BH)_(max)=76.7).SEM results indicate that,on the one hand,950℃is the optimal diffusion *** diffusion temperature results in insufficient diffusion of Tb *** diffusion temperature can lead to the main phase grain growth,the decrease of Nd-rich phase,and forming holes in the *** the other hand,500℃is the optimal annealing *** annealing temperature can result in the reduction of Nd-rich *** annealing temperature can generate the non-defined Nd-rich thin layer between grains.

关键词： Sintered Nd-Fe-B magnets Magnetron sputtering Tb coating magnetic properties Rare earths

magnetic properties of Mn-doped GaN with defects:ab-initio calculations

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Chinese Physics B 2011年第8期20卷 297-303页

作者： E.Salmani A.Benyoussef H.Ez-Zahraouy E.H.Saidi LMPHE Departement de PhysiqueFacult'e des SciencesUniversit'e Mohammed V-AgdalRabatMorocco LPHE Departement de PhysiqueFacult'e des SciencesUniversit'e Mohammed V-AgdalRabatMorocco

According to first-principles density functional calculations, we have investigated the magnetic properties of Mn- doped GaN with defects, Ga1-x-yVGxMny N1-z-tVNzOt with Mn substituted at Ga sites, nitrogen vacancies VN, gallium vacancies VG and oxygen substituted at nitrogen sites. The magnetic interaction in Mn-doped GaN favours the ferromagnetic coupling via the double exchange mechanism. The ground state is found to be well described by a model based on a Mn3＋-d5 in a high spin state coupled via a double exchange to a partially delocalized hole accommodated in the 2p states of neighbouring nitrogen ions. The effect of defects on ferromagnetic coupling is investigated. It is found that in the presence of donor defects, such as oxygen substituted at nitrogen sites, nitrogen vacancy antiferromagnetic interactions appear, while in the case of Ga vacancies, the interactions remain ferromagnetic; in the case of acceptor defects like Mg and Zn codoping, ferromagnetism is stabilized. The formation energies of these defects are computed. Furthermore, the half-metallic behaviours appear in some studied compounds.

关键词： diluted magnetic semiconductor GaN:Mn defects ab-initio magnetic properties

magnetic properties and magnetocaloric effect in Nd_xLa_(1-x)Fe_(11.5)Al_(1.5) compounds

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Chinese Physics B 2008年第8期17卷 3087-3092页

作者：王芳王光军孙继荣沈保根 State Key Laboratory of Magnetism Institute of Physics and Centre for Condensed Matter Physics Chinese Academy of Sciences

Effects of Nd-doping on the magnetic properties and magnetocaloric effects （MCEs） of NdxLa1-xFe11.5Al1.5 have been investigated. Substitution of Nd leads to a weakening of the antiferromagnetic （AFM） coupling and an enhancement of the ferromagnetic （FM） coupling. This in turn results in a complex magnetic behaviour for Nd0.2La0.8Fe11.5Al1.5 characterized by the occurrence of two phase transitions at ～188 K （PM AFM） and ～159 K （AFM-FM）. As a result, a table-like MCE （9 J/kg.K） is found in a wide temperature range （160-185 K） for a field change of 0-5T around the transition temperature, as evidenced by both the magnetic and calorimetric measurements. Based on the analysis of low-temperature heat capacity, it is found that the AFM-FM phase transition modifies the electron density significantly, and the major contribution to the entropy change comes from the electronic entropy change.

关键词： magnetic properties NaZn13-type compounds magnetic entropy change

magnetic properties of Nd_(12)Co_6Pb Compound

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Journal of Rare Earths 2006年第z2期24卷 329-331页

作者：何维张吉亮曾令民 Key Laboratory of Nonferrous Metals and New Processing Technology of Materials Ministry of EducationGuangxi University Institute of Materials Science Guangxi University

The magnetic and magnetocaloric properties for the Nd12Co6Pb compound were investigated. The Curie temperature Tc of the magnetic transition of Nd12Co6Pb compound is 194 K. The experimentally determined magnetic effective paramagnetic moment isμeff= 12.36μB per formula unit (3.49μb per Nd atom). The maximum magnetic entropy change in the low magnetic field changes of 0 ~ 2 T for the Nd12Co6Pb compound is about 215.0 J·mole-1·K-1.

关键词： magnetic properties magnetocaloric effect Nd12Co6Pb rare earths

magnetic properties of Nd_2Fe_(14)B/α-Fe nanocomposite magnets with yttrium addition

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Rare Metals 2010年第3期29卷 265-269页

作者： CHEN Zhi'an SUI Yanli GUO Zhimeng Institute of Powder Metallurgy University of Science and Technology Beijing Beijing 100083 China State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China

The phase evolution and magnetic properties of Nd9？xYxFe72Ti2Zr2B15 （x = 0,0.5,1,and 2） melt-spun nanocomposite ribbons were *** is found that Y addition not only enhances the formability of amorphous phase in the alloy,but also stabilizes the amorphous phase during the annealing *** appropriate content of Y addition effectively enhances the remanence （Jr） of the annealed *** residual amorphous intergranular phase in the annealed sample optimizes the squareness of the loop,resulting in an larger maximum energy product （BH）*** best magnetic properties,Jr = 0.78 T,Hci （coercivity） = 923.4 kA/m,and （BH）max = 98.5 kJ/m3,were obtained from the Nd8YFe72Ti2Zr2B15 ribbon spun at Vs = 4 m/s and annealed at 700°C for 10 min,which is composed of Nd2Fe14B,α-Fe,and amorphous phase.

关键词： magnetic properties nanocomposite yttrium addition formability amorphous phase

magnetic properties and promising cryogenic magneto-caloric performances of Gd_(20)Ho_(20)Tm_(20)Cu_(20)Ni_(20) amorphous ribbons

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Chinese Physics B 2021年第1期30卷 493-496页

作者： Yikun Zhang Bingbing Wu Dan Gu Jiang Wang Zhongming Ren State Key Laboratory of Advanced Special Steels Shanghai UniversityShanghai 200072China Shanghai Key Laboratory of Advanced Ferrometallurgy Shanghai UniversityShanghai 200072China School of Materials Science and Engineering Shanghai UniversityShanghai 200072China

The magnetic cooling utilizing magneto-caloric effect is recognized as promising energy efficiency and environmentally friendly *** we report a systematical study on the microstructures,magnetic properties and cryogenic magneto-caloric performances of the Gd_(20)Ho_(20)Tm_(20)Cu_(20)Ni_(20) amorphous *** is found that the ribbons reveal a second-order phase transition and are accompanied by a table-shaped magneto-caloric *** calculated magneticentropy-change maximum |ΔSM|,temperature averaged entropy change(i.e.,TEC(10)),and refrigerant capacity reach 13.9 J/kg·K,13.84 J/kg-K and 740 J/kg with magnetic field change of 0-7 T,respectively,indicating that the present Gd_(20)Ho_(20)Tm_(20)Cu_(20)Ni_(20) amorphous ribbons are good candidates for magnetic cooling.

关键词： microstructure magneto-caloric effect(MCE) amorphous ribbons magnetic properties

magnetic properties of Perovskite Manganite La_ (0.3)Ca_ (0.7)Mn_ (0.96)W_ (0.04)O_3 in Charge Ordering Phase

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Journal of Rare Earths 2005年第S1期23卷 251-254页

作者：彭振生郭焕银严国清毛强 MR Materials Research Laboratory Suzhou College Suzhou 234000 China Structure Research Laboratory University of Science and Technology of China Hefei 230026 China MR Materials Research Laboratory Suzhou College Suzhou 234000 China

The sample La_ 0.3Ca_ 0.7Mn_ 0.96W_ 0.04O_3 was prepared by the solid-state method. magnetic properties of La_ 0.3Ca_ 0.7Mn_ 0.96W_ 0.04O_3 was studied through the measurement of M-T curve, M-H curves and ESR curves of the sample. The results show that: charge ordering (CO) phase forms at 265 K; the system exhibits paramagnetism when T>265 K; it exhibits long-range anti-ferromagnetism (there is a little FM component in AFM background) and the coexistence of a little FM phase and AFM/CO phase forms when Tmagnetic resonance ΔH_ PP increases with temperature decreasing, which indicates that ferromagnetic connection of the sample strengthens with temperature decreasing.

关键词： manganite La_ 0.3Ca_ 0.7Mn_ 0.96W_ 0.04O_3 charge ordering electron paramagnetic resonance magnetic properties

magnetic properties of Fe_(3(1-x))Cr_(3x)C alloys

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International Journal of Minerals,Metallurgy and Materials 2009年第3期16卷 314-316页

作者： Feng-qi Zhao O. Tegus B. Fuquan E. Brück Inner Mongolia Key Laboratory for Physics and Chemistry of Functional Materials College of Physics and Electron Information Inner Mongolia Normal University Hohhot 010022 China Van der Waals-Zeeman Instituut Universiteit van Amsterdam Valckenierstraat 65 1018XE Amsterdam Netherlands

The magnetic properties of Fe3（1-x）Cr3xC alloys with x=0.05, 0.1, 0.15, and 0.2, which crystallize in the cementite Fe3C-type structure with space group Pnma, were investigated by means of magnetization measurements. These alloys show temperature-induced second-order magnetic phase transitions. The Curie temperature （Tc） of these alloys decreases with increasing x. The isothermal magnetic-entropy changes of these alloys were derived from the magnetic isotherms measured with increasing temperature and increasing field. The maximum values of the magnetic-entropy change are about 0.9 and 3.6 J·kg^-1·K^-1 at Tc =360 K for x = 0.05 in a magnetic field change from 0 to 1 T and 0 to 5 T, respectively.

关键词： magnetic properties magnetocaloric effect magnetic-entropy change magnetic refrigeration