R2Fe14B型永磁材料中第二磁晶各向异性常数对反磁化过程的影响

针对低温下各向同性Pr2Fe14B永磁材料的最小形核场问题,用数值计算法和近似解析解研究了第二磁晶各向异性常数K2对最小形核场的影响.研究发现,尽管对于Nd2Fe14B永磁材料一级近似的解析解与数值计算结果很接近,但是对于低温下各向同性Pr2Fe14B永磁材料则至少要用二级近似下的解析解才能与数值计算结果相接近.用有关最小形核场的计算结果很好地解释了低温时各向同性Pr2Fe14B永磁材料的矫顽力与最小形核场的关系.     

R2Fe14B(R=Ce,Pr,Gd)磁晶各向异性常数K1,K2随温度的变化

本文在1.5—300K温度范围内测量了R₂Fe₁₄B(R=Ce,Pr,Gd)各向异性常数K₁,K₂和各向异性场H_A随温度的变化。同时用单离子模型计算了Pr³⁺离子对Pr₂Fe₁₄B磁晶各向异性的贡献,得到与实验值半定量符合的结果。 关键词：     

纳米晶复合Pr2Fe14B/α-Fe快淬薄带的织构与磁性

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     

取向Pr2Fe14B与Nd2Fe14B多晶磁化曲线的 计算

基于单离子晶场模型,提出了计算稀土-Fe(Co)金属间化合物取向多晶样品磁化曲线的方法.用此方法计算了取向Pr₂Fe₁₄B和Nd₂Fe₁₄ B多晶的高场磁化曲线,计算中使用了拟合化合物单晶磁化曲线得到的交换场与晶场参数.计 算曲线与实验曲线相符合. 关键词： 磁化曲线 晶场 2Fe₁₄B')" href="#">R₂Fe₁₄B     

晶粒易轴取向度对纳米晶永磁Pr2Fe14B磁性的影响

构造了立方和不规则形状晶粒的各向异性纳米晶单相Pr₂Fe₁₄B磁体 .利用微磁学的有限元法，模拟计算了样品的磁滞回线.计算结果表明，随着磁体晶粒易轴取向度的变差， 磁体的剩磁、矫顽力均随之下降.不同晶粒尺寸的纳米晶单相Pr₂Fe_{14B磁体，其磁 性能随取向度的变化快慢不同，原因在于磁体中的晶间交换作用 (IGEC) 的强弱不同.随着 晶粒取向度的提高，纳米晶单相磁体的矫顽力逐渐增加，这完全不同于烧结磁体. 关键词： 纳米晶磁体 矫顽力 剩磁}     

纳米晶复合Pr2Fe14B/α-Fe永磁材料磁性的研究

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(Pr_xFe_94.3-xB_5.7)_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. 关键词： 纳米复合永磁材料 熔体快淬 2Fe₁₄B/α-Fe')" href="#">Pr₂Fe₁₄B/α-Fe 磁性     

Nd2Fe14B化合物磁晶各向异性起源的理论研究

本文根据Nd₂Fe₁₄B化合物中存有少量巡游电子的基本实验事实,提出了在Nd₂Fe₁₄B中配位子所产生的晶场和巡游电子所产生的电场共同造成了Nd离子磁晶各向异性的理论模型。提出并解决了计算巡游电子同中心Nd离子相互作用的理论方法。在同时考虑Nd离子所受配位子的晶场和巡游电子的电场的作用情况下,用单离子模型计算了Nd₂Fe₁₄B中Nd离子所产生的磁晶各向异性及其随温度的变化。所 关键词：     

复相Nd4.5Fe76.3Ga0.3Co1.0B18合金的结构与磁性

利用快淬法制备了Nd_4.5Fe_76.3Ga_0.3Co_1.0B₁₈非晶合金,晶化处理后获得主相为Fe₃B与Nd₂Fe₁₄B的纳米晶永磁材料.采用X射线衍射、透射电子显微镜及磁测量手段分析研究了材料的微观结构与磁性能,并通过测量磁体的δM曲线,研究了晶粒间的交换耦合作用及其与微观结构、磁性能的关系. 关键词：     

纳米复合永磁Pr9Fe74Co12B5Snx(x=0, 0.5)的磁化行为与磁黏滞性

用熔体快淬法制备了纳米复合永磁样品Pr₉Fe₇₄Co₁₂B₅ 与Pr₉Fe₇₄Co₁₂B₅Sn_0.5，分析了样品的起始磁化、反磁化过程，测得样品的总磁化率、可逆磁化率以及样品的磁黏滞性.结果表明，两样品在室温下均表现为单一硬磁相磁化行为，在低温下表现为双相行为，且由于添加Sn后使晶粒均匀化从而导致样品低温下的双相行为更加明显.添加Sn后引起样品中软磁相含量和软磁相晶粒尺寸的增加，使磁化反转中可逆磁化部分增多，且使反磁化形核场降低.磁黏滞性研究表明，热激活体积与软磁相晶粒的大小有关. 关键词： 纳米复合永磁 磁化反转 磁粘滞     

Ti掺杂Nd2Fe14B/α-Fe纳米双相复合永磁体晶化动力学

纳米双相复合稀土永磁材料,利用硬磁相高磁晶各向异性和软磁相高饱和磁化强度的优点,通过铁磁交换耦合作用获得优异的磁性能.但是如何解决软硬磁双相纳米微结构不匹配的问题,控制软硬磁相同时达到理想的纳米尺度复合是关键.本文研究了掺杂合金元素Ti对熔体快淬法制备的Nd₂Fe₁₄B/α-Fe快淬薄带晶化过程的影响.结果表明,掺杂合金元素Ti能影响Nd₂Fe₁₄B/α-Fe交换耦合磁体整个晶化动力学过程,使α-Fe相的晶化激活能升高,抑制其从非晶相中析出.同时,降低1∶7亚稳相的晶化激活能,起到稳定亚稳相的作用.而且随着晶化温度的进一步提高, α-Fe和Nd₂Fe₁₄B两相由1∶7亚稳相分解产生,从而有效避免了α-Fe相的优先析出.显微组织观察表明,掺杂Ti的样品晶粒细小、分布均匀,平均晶粒尺寸在20 nm左右,没有特别大的α-Fe粒子出现.当Ti的掺杂量原子百分数为1.0%时,获得了最佳磁性能(BH)_max=12 MG·Oe(1 G=10     

Synthesis,structures and magnetic properties of Pr-lean Pr2Fe14B/Fe3B nanocomposite alloys

The lean rare-earth Pr_4.5Fe_77−xTi_xB_18.5 (x=0, 1, 4, 5) nanocomposite alloys were prepared by melt spinning method and subsequent thermal annealing. The effect of Ti content and annealing temperature on the magnetic properties and the microstructure of these magnets were investigated. The enhancing coercivity H_c from 211.4 to 338.2 kA/m has been observed at the optimal annealing temperature of 700 °C by the addition of 5 at% Ti in Pr₂Fe₁₄B/Fe₃B alloys. It was also found that increasing Ti content leads to marked grain refinement in the annealed alloys, resulting in strong exchange-coupling interaction between the hard and the soft phases in these ribbons. In addition, the magnetization reversal behaviors of Pr₂Fe₁₄B/Fe₃B nanocomposites were discussed in detail.     

磁共振法研究(Fe1-xCox)84Zr3.5Nb 3.5B8Cu1纳米晶薄带的磁各向异性

铁磁共振（FMR）实验研究(Fe_1-xCo_x)₈₄Zr_{3.5 Nb3.5B8Cu1（x=0.0,0.2,0.4,0.6, 0.8）合金薄 带的各向异性，易轴在薄带的横向方向,同等宽度样品 的各向异性常数K′随Co掺杂量的增加而减小, K′值在4.67×10^-5　J/m（x=0. 0）到 2.54×10^-5　J 关键词： 铁磁共振 各向异性常数 低场非共振信号 磁化过程}     

Sono-enhanced degradation of dye pollutants with the use of H2O2 activated by Fe3O4 magnetic nanoparticles as peroxidase mimetic

Sono-enhanced degradation of a dye pollutant Rhodamine B (RhB) was investigated by using H₂O₂ as a green oxidant and Fe₃O₄ magnetic nanoparticles (MNPs) as a peroxidase mimetic. It was found that Fe₃O₄ MNPs could catalyze the break of H₂O₂ to remove RhB in a wide pH range from 3.0 to 9.0 and its peroxidase-like activity was significantly enhanced by the ultrasound irradiation. At pH 5.0 and temperature 55 °C, the ultrasound-assisted H₂O₂–Fe₃O₄ catalysis removed about 95% of RhB (0.02 mmol L⁻¹) in 15 min with a apparent rate constant of 0.15 min⁻¹ for the degradation of RhB, being 6.5 and 37.6 folds of that in the simple catalytic H₂O₂–Fe₃O₄ system, and the simple ultrasonic US-H₂O₂ systems, respectively. The beneficial synergistic behavior between Fe₃O₄ catalysis and ultrasonic was demonstrated to be dependent on Fe₃O₄ dosage, H₂O₂ concentration, pH value and temperature. As a tentative explanation, the observed significant synergistic effects was attributed to the positive interaction between cavitation effect accelerating the catalytic breakdown of H₂O₂ over Fe₃O₄ nanoparticles, and the function of Fe₃O₄ MNPs providing more nucleation sites for the cavitation inception.     

Superconductivity of powder-in-tube Sr0.6K0.4Fe2As2 wires

Nb-sheathed Sr_0.6K_0.4Fe₂As₂ superconducting wires have been fabricated using the powder-in-tube (PIT) method for the first time and the superconducting properties of the wires have been investigated. The transition temperature (T_c) of the Sr_0.6K_0.4Fe₂As₂ wires is confirmed to be as high as 35.3 K. Most importantly, Sr_0.6K_0.4Fe₂As₂ wires exhibit a very weak J_c-field dependence behavior even the temperature is very close to T_c. The upper critical field H_c2(0) value can exceed 140 T, surpassing those of MgB₂ and all the low temperature superconductors. Such high H_c2 and superior J_c-field performance make the 122 phase SrKFeAs wire conductors a powerful competitor potentially useful in very high field applications.     

Torque magnetometer measurements of the temperature dependence of induced anisotropy energy and of saturation magnetization in amorphous Fe40Ni40P14B6

Induced anisotropy energy K_u and saturation magnetization M have been measured as a function of temperature T between 77 K and T_c on co$\text{n}$venient specimens of amorphous Fe₄₀Ni₄₀P₁₄B₆ by means of a torque magnetometer. The M vs. T curve is found to follow an anomalously low behaviour with respect to crystalline materials. The exper$\text{i}$mental K_u vs. T curve is well fitted by a M² law, also different from higher power laws typical of crystalline alloys.