Mechanisms of High Coercivity in Ni/NiO Composite Films by Post Annealing

A coercivity as large as 2.4 kOe has been achieved in the Ni/NiO composite film after an annealing under a magnetic field of 10 kOe and an O2 partial pressure of 0.001 torr. The coercivity was attributed to the strong exchange coupling of Ni and NiO. Small grain size of Ni and NiO was observed after the post-annealing. The enhanced coercivity is probably associated with the domain wall pinning by local energy minima, the distribution of Ni and NiO, and the domain structure in the interface of Ni/NiO generated under the presence of the magnetic field during the post-annealing.     

Nd2Fe14B/α-Fe纳米晶复合永磁材料的计算机模拟研究

采用计算机模拟的方法计算了 Nd2 Fe1 4B/α- Fe纳米晶复合永磁材料的磁性能 ,并对软磁相比例及不规则晶粒对磁性能的影响进行了研究。结果显示 ,当软磁相比例增加时 ,由于软磁相高的饱和磁极化强度以及软硬磁相间的交换耦合作用的影响 ,剩磁逐渐增加 ,但矫顽力则随着软磁相的增加而逐渐下降。不规则晶粒对磁体的剩磁基本没有影响 ,但降低矫顽力。     

Characterisation of bubble materials

The rapid development of magnetic bubble technology has required growth to exacting specifications of a large number of magnetic films of garnets and some amorphous binary and ternary alloys of rare-earth and transition metals. The characterisation of these films is an essential part in the search for newer materials which hold out promise for better device performance and cost viability. Many methods of films characterisation have been reported from time to time. By and large, these methods can be divided into two groups: one, bulk measurements made on the film and two, measurements made on the domains. We have attempted to collate and briefly introduce various techniques to characterise magnetic bubble materials in this review.     

Effect of Copper and Titanium Addition on Microstructures and Magnetic Properties of Sintered Nd_(22) Fe_(71) B_7 Magnets

Ｉｔｉｓｗｅｌｌｋｎｏｗｎｔｈａｔｔｈｅｉｎｔｅｒｇｒａｎｕｌａｒｍｉ ｃｒｏｓｔｒｕｃｔｕｒｅｏｆｓｉｎｔｅｒｅｄＮｄ Ｆｅ Ｂｍａｇｎｅｔｓｐｌａｙｓａｋｅｙｒｏｌｅｉｎｄｅｔｅｒｍｉｎｉｎｇｔｈｅｉｒｃｏｅｒｃｉｖｉｔｙａｎｄｔｈｅｒｍａｌｓｔａｂｉｌｉｔｙ[1,2 ] .Ｔｈｅｒｅｆｏｒｅ ,ｉｔｉｓｉｍｐｏｒ ｔａｎｔｔｏｆｕｒｔｈｅｒｍｏｄｉｆｙｉｎｇｔｈｅｉｎｔｅｒｇｒａｎｕｌａｒｍｉ ｃｒｏｓｔｒｕｃｔｕｒｅｖｉａａｌｌｏｙｉｎｇｏｒｏｔｈｅｒｐｒｏｃｅｓｓｉｎｇｍｅｔｈｏｄｉｎｉｍｐｒｏｖｉ…     

磁控溅射Fe-N单层膜的研究

本文研究了在不同温度的基片上进行磁控溅射,氮流量对Ｆｅ－Ｎ薄膜的磁性和结构的影响。实验表明,基片温度为２００℃有助于提高Ｆｅ－Ｎ薄膜的办磁性能,基片为曙和１００℃,氮流量在０～２ｓｃｃｍ范围内变化时,未发现ｒ－Ｆｅ４Ｎ和ａ－Ｆｅ１６Ｎ２,薄膜中只有Ｎ在ａ－Ｆｅ蝇的固溶体。基片温度２００℃,氮流量大于１．０ｓｃｃｍ时,薄中出现ｒ－Ｆｅ４Ｎ,但仍未发现ａ－Ｆｅ１６Ｎ２,加氮后薄膜的软磁性能明显小于纯铁     

Oxide evolution in NdDy-Fe-B magnet during aging process

Sintered NdDy-Fe-B magnets were made from strip cast flakes by powder metallurgy method. For the magnet with 6wt.% Dy substituted Nd, a remarkable coercivity increase of 70% was obtained after aging at 900°C for 2h and a high coercivity of 23.5 kOe was achieved after aging at 520°C for 2h. The average diameter of the oxide particles decreased during the following 900°C aging treatment. Dy and O diffusion from oxide particles to Nd-rich phase during the aging process was observed. The oxide evolution and Dy element diffusion were helpful to the coercivity enhancement.     

Crystal structure,microstructure and magnetic properties of SmCo-based films treated by different annealing methods

Effect of conventional thermal annealing(CTA) and rapid recurrent thermal annealing(RRTA) processes on crystal structure,mi-crostructure,and magnetic properties of the SmCo-based films were investigated.The results indicated that the CTA-treated films exhibited poor permanent magnetic properties,and a low intrinsic coercivity of 72.8 kA/m was observed.Wide hysteresis loop was obtained for the RRTA-treated films,providing better permanent magnetic properties.The intrinsic coercivity reached 312.0 kA/m.According to the X-ray diffraction(XRD) and atomic force microscopy(AFM) results,the magnetic properties of the CTA-treated films and RRTA-treated films were found to be correlated with the crystal structure and microstructure,which were strongly determined by the annealing treatment.CTA treatment led to poor crystallization effects for the films,and a rough surface(RMS=3.47 nm and P-V=35.42 nm) and large grain size of 92.7 nm were observed correspondingly.However,the RRTA treatment exhibited great contributions on the crystallization of the films,which is accountable for the smooth surface(RMS=2.047 nm and P-V=16.43 nm) and fine grain size of 60.8 nm.     

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 针对目前只能检测软磁材料标准环形样或棒状样品，不能检测异形件质量这一问题，设计了相关的试验，针对软磁材料1J50，通过差值对比法，找到合格与不合格异形件之间矫顽力差值最大的条件，达到检测异形件质量的目的。试验分析了不同磁化电流、不同制样方法、不同样品模块下矫顽力测量差值。试验结果表明，在450、500 mA的磁化电流下，反向电流分别在7，5 mA左右，在这些点，加不合格样与加合格样的两条曲线有明显的不同之处，因此可以达到区分合格品与不合格品的目的。     

利用共伴生混合稀土制备RE-Fe-B永磁材料

利用白云鄂博共伴生混合稀土(MM)制备了成分为(Pr Nd)14-x MMx Fe80.4B5.6的稀土永磁材料,MM替代30%Pr Nd合金,磁体磁能积为238.08 k J/m3,剩磁为1.18 T,矫顽力726.75 k A/m,发现La、Ce元素以氧化物的形式分布在富稀土相中,主相中存在(Nd Ce)2Fe14B固溶体,相比单独添加La、Ce的磁体,获得相同的磁性能时,(Pr Nd)14-x MMx Fe80.4B5.6磁体的La含量较高,磁体中混合稀土La、Ce、Pr、Nd的协同作用促进了MM的高效利用。利用高场动态磁畴显微镜观察了磁体的畴结构动态变化,磁体内部出现大量的穿晶畴,穿晶畴的畴壁可穿过晶界,磁化过程中磁畴扩展容易。     

Intrinsic Coercivity of SmCo Based Permanent Magnetic Films Prepared on Hot Substrates at 650 ºC

以Al、Cu、Ag、Mo、Cr为衬底层,在650 ℃热硅基片上制备了未经后退火工艺处理的SmCo基永磁薄膜,研究了薄膜内禀矫顽力的变化规律。结果表明,采用Mo和Cr作为衬底层可以提高薄膜的内禀矫顽力。SmCo基永磁薄膜的厚度对内禀矫顽力的影响复杂,当薄膜厚度为3.0 μm时,可以获得室温内禀矫顽力的最大值为281.6 kA·m-1。内禀矫顽力的温度依赖关系主要取决于薄膜的相关磁学参数,在25～300 ℃范围内,内禀矫顽力高于200 kA·m-1