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.     

辊速及晶化工艺对(Nd, Pr)13Fe80Nb1B6快淬薄带组织和矫顽力的影响

用熔体快淬法制备(Nd,Pr)_(13)Fe_(80)Nb_1B_6快淬薄带并晶化处理,研究辊速和晶化条件对其组织和矫顽力的影响.结果表明,在10～20、25和35 m/s分别得到纳米晶、部分非晶和完全非晶薄带,且在18 m/s制备的薄带有较好的c轴各向异性.快淬态薄带的矫顽力随辊速(10～25 m/s)的增大而增加.非晶薄带晶化后由(Nd,Pr)_2Fe_(14)B相和富稀土相组成,且完全非晶薄带晶化后比部分非晶薄带晶化后的矫顽力要高,这是由于前者比后者具有更均匀的微结构造成的.非晶薄带晶化后矫顽力最大为1616 kA/m,高的矫顽力与添加Pr和Nb有关.     

Effects of Ag layers on the SiO2/FePt thin films deposited by magnetron sputtering

The effects of Ag layers with different locations and thicknesses on the structural and magnetic property of SiO2/FePt multilayer films were investigated.The non-magnetic Ag layer plays an important role in inducing（001） orientation and ordering of FePt grains,as well as the SiO2-doping reducing the grain size and the magnetic exchange coupling between grains.When the 10 nm Ag layer is moved from the bottom to the top of the SiO2/FePt multilayer film,the coercivity gradually decreases;the largest difference between the out-of-plane coercivity and the in-plane one is obtained in the sample of [SiO2（2 nm）/FePt（3 nm）]3/Ag（10 nm）/[SiO2（2 nm）/FePt（3 nm）]2.Furthermore,the location of Ag layers was fixed and the thickness was changed.The XRD curves suggest that the intensity of the（001） peak becomes the strongest with the addition of 10 nm Ag layers.     

Temperature stability and microstructure of ultra-high intrinsic coercivity Nd-Fe-B magnets

The variations of intrinsic coercivity and remanence of sintered Nd-Fe-B magnets with ultra-high intrinsic coercivity were investigated. The results showed that the intrinsic coercivity and remanence declined simultaneously with increasing temperature, but the squareness of the magnets has hardly been changed. The temperature coefficients of remanence （α） and coercivity （β） for the magnets were calculated by two different methods, and the variations of the temperature coefficients and the microstructure of sintered Nd-Fe-B magnets were analyzed. The temperature coefficients of remanence （α） and coercivity （β） for the sintered magnets are very small, and the existence of fine microstructure is necessary to obtain sintered Nd-Fe-B magnets with ultra-high intrinsic coercivity.     

Sm2Co17型高温稀土永磁的微结构与磁性能

采用透射电子显微镜（TEM）、扫描电子显微镜（SEM）、磁力显微镜（MFM）和原位X射线衍射（XRD）等探讨Sm2Co17型稀土永磁材料的胞状结构、畴结构和相结构及其对磁性能的影响,制备使用温度为500℃的高温稀土永磁材料。结果表明,Sm（CoFe0.11Cu0.10Zr0.03）7.5具有很好的高温稳定性,500℃时的磁性能为：Br=0.708 T,Hci=646.7 kA/m,BHmax=85.4 kJ/m^3;其磁畴宽度远小于晶粒尺寸,但大于胞状结构的尺寸,使用温度较高的磁体具有较小的磁畴和胞状结构;当使用温度小于300℃时,Sm2Co17型磁体内存在的相结构为2：17R、2：17H和1：5相,矫顽力主要受1：5相的钉扎而产生;当300℃〈t〈tc^1：5时,部分1：5相转变成中间相并最终转变成2：7相,磁体的矫顽力将由1：5相钉扎和2：7相形核所控制;当t≥tc^1：5时,磁体的矫顽力将全部由非磁性1：5相和2：7相形核所控制。     

交换耦合双层膜NiO/Ni81Fe19的基片温度效应研究

用射频磁控溅射方法在不同基片温度下玻璃基片上分别制备NiO单层膜、NiFe单层膜和NiO／NiFe双层膜,研究了不同基片温度对膜的磁性能的影响．用振动样品磁强计（VSM）分析了膜的磁特性,结果表明：基片温度260℃时淀积的NiFe膜矫顽力Hc为184A·m^－1,小于室温淀积NiFe膜的H_c（584A·m^－1）,且磁滞回线的矩形度更好．室温下淀积NiO（50nm）／NiFe（15nm）双层膜的Hc为4000A·m^－1,交换耦会场（H_EX）仅为1600A·m^－1,磁滞回线的短形度很差,而260℃时淀积的双层膜的Hc下降到3120A·m^－1,H_EX却增大为4640A·m^－1,同时磁滞回线的矩形度也得到改善,其截止温度T_B高达230℃．X射线衍射（XRD）分析了膜的织构,结果表明：室温下淀积NiO膜呈现（220）织构,而260℃时淀积NiO膜呈现（111）织构;室温和260℃淀积的NiFe膜都呈（111）织构,但后者晶粒比前者大．     

A NOVEL ROUTE FOR MAKING COERCIVE NdFeB POWDER——HDD PROCESS

NdFeB coercive powder can be obtained directely by hydrogen treated ahoy ingots,The magnetic properties of the powder are comparable with that made by rapidsolidifiedprocess.An appreciable coercivity created during hydrogen treatment is closely relatedto the refined crystal grains.     

THREE NEW Fe-BASED MICROCRYSTALLINE ALLOYS WITH SUPERIOR MAGNETIC PROPERTIES

Three new Fe-based microcrystalline alloys,i.e.,Fe_(73.1)Cu_(1.2)Nb_(3.2)Si_(12 5)B_(10),Fe_(73)Cu_1Nb_(1.5)Mo_2Si_(12.5)B_(10) and Fe_(73)Cu_1Zr_3C_(0.5)Mo_Si_(12.5)B_(10),were developed with su-perior magnetic properties.e.g.,high relative initial permeability of μ_i~15×10~4,lowcoercivity of H_c1.0A/m,high effective permeability and low core losses in a consid-crable wide frequency range and high pulse-magnetic permeability under narrow pulse.The optimum value of relative effective permeability,μ_5~1 is 16×10~4 under condition off=1 kHz and H_m=0.4 A/m.The optimum values of core loss reach 57.9 30.2 and 68W/kg under condition of f=50.100.100 KHz and B_m=0.5,0.2,0.3 T,respectively.These three alloys have superior stability of magnetic properties.Initial permeabilitymay be not changed during heating at 130℃ up to 216 h.The main crystalline phaseis ordered phase Fe_((75)+y)Si_((25)-y) which is ultrafine particles of average size 10—20 nm.