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61.
INTER-GRAIN EXCHANGE INTERACTION FOR SINGLE-PHASE NANOCRYSTALLINE Nd-Fe-B MAGNETS 总被引:1,自引:0,他引:1 下载免费PDF全文
The demagnetization curve as a function of intensity of the inter-grain exchange interaction was calculated for single-phase nanocrystalline Nd-Fe-B magnets by use of the finite-element technique of micromagnetics. Also, the strength of the exchange interaction was estimated as a function of the Nd content x for the nanocrystalline NdxFe94-xB6 magnets by comparing the above result with the experimental relation between iHc and x for the magnets. We found that the inter-grain exchange interaction decreases with the increase of x, are ≈70% and ≈60% of the inter-grain exchange interaction for x=15.5(μ0iHc≈2.0T) and x=19(μ0iHc≈2.3T), respectively. 相似文献
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63.
M. Büttner P. WeberC. Lang M. RöderD. Schüler P. GörnertP. Seidel 《Journal of magnetism and magnetic materials》2011,323(9):1179-1184
We investigated the magnetic properties of two kinds of magnetosomes (25-42 nm) produced by the magneto-tactic bacterium Magnetospirillum gryphiswaldense. At temperatures between 4.2 K and room temperature the temperature dependent magnetorelaxation (TMRX) method was used. We found three areas with magnetic signals and discuss them in this paper using the results of additional hysteresis loop measurements. The signals detected above 300 K show the lower end of a beginning energy barrier distribution. The signals between 70 and 120 K lie in the area of the Verwey transition and disappear over time due to aging processes. In addition to these signals, other signals at temperatures between 4.2 and 70 K were found and possible causes are discussed. 相似文献
64.
L.A.S. de Oliveira J.P. SinneckerR. Grössinger A. Pentón-MadrigalE. Estévez-Rams 《Journal of magnetism and magnetic materials》2011,323(14):1890-1894
We investigate the influence of Cu substitution, on the coercivity and magnetic viscosity, in the ternary system GdCo5−xCux (x=0, 0.5, 1, 1.5, 2 and 2.5) with different field sweep rates. All samples have been studied in the as cast state and crystallize in a single phase CaCu5 structure. With Cu addition, the coercivity was 10 times enhanced for x =1.5. The behavior of the coercivity Hc against field sweep rate, dH/dt, shows that the GdCo5−xCux system exhibits only a small magnetic viscosity effect, a desirable property for magnetic dynamic applications under high magnetic field. 相似文献
65.
对Sm(CobalFe0.1Cu0.1Zr0.033)6.9合金, 经810℃等温时效后以0.5℃/min逐渐冷却, 在600℃-400℃温度区间淬火, 研究了不同淬火温度下的磁滞回线、磁畴和矫顽力温度系数β. 发现时效600℃淬火后磁滞回线出现台阶状, 说明畴壁中应存在两处钉扎. 随淬火温度的降低, 合金的室温矫顽力显著增加, 磁滞回线的台阶消失. 通过磁畴形貌发现时效600℃淬火后的磁畴接近条形畴, 1:5相中Cu分布相对均匀, 形成的畴壁钉扎较弱, 从而使磁滞回线出现台阶, 决定矫顽力的畴壁钉扎位于两相界面处; 随时效淬火温度的降低, 磁畴逐渐细化, 畴壁1:5相中的畴壁能降低, 形成了较强的内禀钉扎, 并决定材料的矫顽力, 两相界面处的畴壁钉扎被掩盖. 对不同温度淬火合金的高温矫顽力研究表明, 最强的畴壁钉扎位于两相界面处时, 矫顽力随温度升高逐渐增加, 矫顽力出现温度反常现象; 最强的畴壁钉扎位于1:5相中心时, 矫顽力随温度升高逐渐衰减. 当测试温度达到500℃后不同淬火温度样品的矫顽力几乎相同, 此时最强畴壁钉扎均在两相界面处. 相似文献
66.
Marek Galewski 《Journal of Difference Equations and Applications》2013,19(10):1441-1453
We investigate the dependence on parameters for second-order difference equations with two-point boundary value conditions using a variational method in case when the corresponding Euler action functional is coercive. Some applications for discrete Emden–Fowler equation are also given. 相似文献
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68.
在氧化铝模板的纳米孔洞中, 用电化学的方法沉积铁镍合金纳米线,经过550℃30h氧化处理 , 成功制备出 NiFe2O4纳米线阵列. 分别用扫描电子显微镜 (SEM) 、透射电 子显微镜 (TEM) 、x射线衍射仪 (XRD) 和振动样品磁场计 (VSM) 对样品的形貌、晶体结构 和磁学性质进行了表征测试. SEM和TEM观察结果显示氧化铝模板的孔洞分布均匀,孔心距约 为110nm; 纳米线的直径约为70nm. XRD显示纳米线阵列的物相结构为NiFe2O4; VSM测试结果表明,NiFe2O4纳米线阵列膜的易磁化方向垂直于膜面. 当垂直 磁化时磁滞回线的矩形比约为05,矫顽力为41×103A/m,比氧化处理前的铁镍合金 纳米线阵列都有显著提高.
关键词:
纳米线
Ni Fe2O4
矫顽力 相似文献
69.
采用能量极小原理的微磁学及Monte Carlo方法对铁磁/反铁磁混合磁性薄膜的磁特性进行了模拟计算,研究了基态下系统的磁滞回线、自旋组态及铁磁交换作用常数JAA、单轴各向异性常数K、偶极相互作用常数D和铁磁性原子掺杂量X对矫顽力Hc的影响. 同时还模拟计算了矫顽力Hc的温度特性.模拟结果表明,在混合磁性薄膜中磁滞回线存在明显的阶梯效应,利用简单的Ising模型揭示这种阶梯效应主要起源于包含不同反铁磁原 子的掺杂量的不同尺寸的原子团对外加磁场所产生不同响应;在基态下当0.5≤X≤1.0时矫顽力Hc随K,J
关键词:
蒙特卡罗
微磁学
阶梯效应
混合磁系统
矫顽力 相似文献
70.
Minimal Coercivity Conditions and Exceptional Families of Elements in Quasimonotone Variational Inequalities 总被引:3,自引:0,他引:3
Bianchi M. Hadjisavvas N. Schaible S. 《Journal of Optimization Theory and Applications》2004,122(1):1-17
A coercivity condition is usually assumed in variational inequalities over noncompact domains to guarantee the existence of a solution. We derive minimal, i.e., necessary coercivity conditions for pseudomonotone and quasimonotone variational inequalities to have a nonempty, possibly unbounded solution set. Similarly, a minimal coercivity condition is derived for quasimonotone variational inequalities to have a nonempty, bounded solution set, thereby complementing recent studies for the pseudomonotone case. Finally, for quasimonotone complementarity problems, previous existence results involving so-called exceptional families of elements are strengthened by considerably weakening assumptions in the literature. 相似文献