高矫顽力2:17型SmCo永磁合金的显微组织分析

制备了具有高矫顽力的2:17型SmCo磁体,采用透射电子显微镜对所制得的具有高矫顽力、低温度系数的2:17型磁体的微观组织进行了研究。结果表明:该磁体具有胞状显微组织,胞内为菱方结构的2:17相,胞壁为六方结构的1:5相,具有六方结构的2:17相位于胞状组织的内部;整齐、完整的胞状组织是获得高性能磁体的必要条件;胞状组织的尺寸大小和各元素在各相中的分布是决定矫顽力大小的关键因素。     

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.…     

Effect of film thickness on magnetic properties of Cr/SmCo/Cr films

Cr/SmCo/Cr films with different SmCo thickness were deposited on glass substrates by magnetron sputtering,followed by an annealing process at 550 °C for 20 min.Experimental results showed that the SmCo film of 30 nm exhibited two-phase behavior in the demagnetization process,the obvious kink was observed near zero.For the SmCo film of 50 nm,the kink was invisible,and a single phase like behavior was obtained in the demagnetization process.The reversal behavior became consistent in the thicker films.Moreover,the coercivity reduced and the saturated magnetization increased obviously with the increasing thickness.X-ray diffraction results indicated that the average grain size of SmCo 5 in the thicker films were almost 30 nm,but the quantity of SmCo 5 grains increased with the increasing thickness,which enhanced the intergrain exchange coupling(IEC) of the SmCo 5 hard phases.The increase of IEC improved the magnetic properties of SmCo films with increasing thickness.     

Structural and magnetic properties of Sm（Co0.7Fe0.1Ni0.12Zr0.04B0.047.5） melt spun isotropic and anisotropic ribbons

We investigated the structural and magnetic properties of Sm(Co0.7Fe0.1Ni0.12Zr0.04B0.04)7.5 melt spun ribbons. Samples were arc melted then melt spun at 37 m/s up to 55 m/s to obtain ribbon for powdering. Annealing was performed in argon atmosphere for 30- 75 min at 600-870 oC. In as-spun ribbons the hexagonal SmCo7 (TbCu7-type of structure) of crystal structure was determined from x-ray diffraction patterns, while fcc-Co has been identified as a secondary phase. After annealing, the 1:7 phase of the as-spun ribbons transformed into 2:17 and 1:5 phases. X-ray patterns for as-milled powders exhibited very broad peaks making it difficult to identify a precise structure but repre-sented the 1:7 structure after annealing at low temperature (650 oC). TEM analysis showed a homogeneous nanocrystalline microstructure with average grain size of 30-80 nm. Coercivity values of 15-27 kOe were obtained from hysteresis loops traced up to a field of 5 T. The co-ercivity decreased as temperature increases, but it maintained values higher than 5 kOe at 380 oC. The maximum energy product at room temperature increased, as high as 7.2 MGOe, for melt-spun isotropic ribbons produced at higher wheel speeds. Anisotropic ribbons had a maximum energy product close to 12 MGOe.     

Effect of Ti cap layer thickness on microstructures and magnetic properties of Ti/Ni/Ti films

Nanogranular Ti(3 nm)/Ni(30 nm)/Ti(t nm )(t=1,3,5,7,10) films were prepared by facing magnetron sputtering from Ti and Ni onto glass substrates at room temperature.The structural and magnetic properties of films strongly depended on the Ti layer thickness.X-ray diffraction(XRD) patterns of all as-deposited films showed strong FCC Ni(111) peak.Vibrating sample magnetometer(VSM) measurements indicated that the perpendicular coercivity of the Ti(3 nm)/Ni(30 nm)/Ti(3 nm) film reached about 36 kA/m.With the increase of Co layer thickness,coercivity(Hc) first increased and then decreased.The grain size and magnetic clusters slightly increased and the value of roughness(Ra) was smallest at t=3 nm.     

Annealing behavior of electroplated permalloy thin films. II

The isochronal and isothermal annealing behavior of electroplated Ni-Fe thin films in the temperature range 373°–773°K has been investigated through measurements of electrical resistivity, coercivity, and relative permeability. Analysis of the experimental data indicates that the resistivity decrease is characterized by an activation energy of about 0.70 eV for temperatures up to 550 ° K, and by an activation energy of about 1.82 eV above this temperature. The coercivity initially decreases with an activation energy of about 0.71 eV, and then increases with activation energies up to 1.81 eV. The relative permeability decreases with an activation energy of 1.01 eV. The significance of these activation energies is discussed in terms of structural changes, and the results are compared with the annealing behavior of vapor deposited Ni-Fe thin films.     

Cr底层中添加Ti对SmCo薄膜磁学性能的影响

采用直流磁控溅射法制备了SmCo/Cr,SmCo/CrTi 和SmCo/CrTi/Cr 系列薄膜。SmCo 薄膜的XRD 结果表明:在Cr 底层中添加Ti,得到的CrTi,CrTi/Cr 底层也是以(110)面择优取向的,但是和Cr 底层相比,衍射峰的位置由44.39°偏移到44.19°。薄膜的磁学性能由振动样品磁强计(VSM)测定,分析VSM 的测量结果可知,用CrTi 和CrTi/Cr做底层,SmCo 薄膜的矫顽力Hc、矩形比S、矫顽力矩形比S*的值都比Cr 底层的大,并且磁反转体积V*的值比Cr 底层的小。SmCo 薄膜的δM(H)曲线说明,Cr 做底层时,薄膜晶粒间的相互作用为极化作用,CrTi,CrTi/Cr 做底层时,薄膜晶粒间的相互作用为交换耦合相互作用。     

The influence of silicon content on physical properties of non-oriented silicon steel

Electric motors make up a large portion of our global electricity consumption and have enjoyed a long history doing so. Electrical steels are popularly used materials in electric motors to improve their performance. This has made them prime candidates for increasing the energy efficiency of electric motors, especially given concerns regarding energy conservation. Now manufacturers of electrical steels have been prompted to seek increasingly efficient electrical steels to provide a more competitive product. This literature review focuses on one specific metallurgical aspect – the defining trait of electrical steels; silicon content and its resulting influence on the physical properties. From the literature review it is concluded that the application requirement and functionality must be considered thoroughly when deciding silicon content.

This review was submitted as part of the 2017 Materials Literature Review Prize of the Institute of Materials, Minerals and Mining run by the Editorial Board of MST. Sponsorship of the prize by TWI Ltd is gratefully acknowledged     

Microstructure and magnetic properties of FePt/MgO multilayers deposited by RF magnetron sputtering

FePt (50 nm) and [FePt(a nm)/MgO(b nm)]5/glass (a=1, 2, 3; b=1, 2, 3) films were prepared by radio frequency (RF) magnetron sputtering technique, and then were annealed at 600°C for 30 min. The effect of MgO layer thickness on the structures and magnetic properties of the FePt/MgO multilayers was investigated. The coercivities and inter-grain interactions of the FePt/MgO films were decreased, yet the degree of (001) texturing drastically increased with the increase in MgO layer thickness when the FePt layer thickness was fixed. Thus, the FePt/MgO films with appropriate coercivities, high perpendicular anisotropy, and weak in-ter-grain interactions were obtained by controlling the MgO layer thickness. Overall, these results indicate that the FePt/MgO nanos-tructured films are promising candidates for future high-density perpendicular recording media.     

Crystallization behaviour and high coercivity of （Nd,Pr）（13）Fe（80）Nb1B6 melt-spun ribbons

Amorphous (Nd,Pr)₁₃Fe₈₀Nb₁B₆ ribbons were crystallized at 670–730°C for 5–25 min to study the effects of isothermal crystallization on their behavior and magnetic properties. XRD results indicate that the isothermal incubation time is 12, 5, and less than 5 min at 670, 700, and 730°C, respectively. High coercivities, with the maximum value of _i H _c = 1616 kA/m at 700°C for 19 min, measured by a physical property measurement system, are obtained in the crystallized ribbons. This is mainly attributed to the addition of Pr and Nb, because Pr₂Fe₁₄B has a higher anisotropic field than Nd₂Fe₁₄B, and Nb enriched in the grain boundary regions can not only reduce the exchange-coupling effects among hard grains, but also impede grain growth during the crystallization process. In addition, it should also be related to the characteristics of the furnace that the authors designed.