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1.
实验研究了第二类哑铃畴在直流偏场和面内场联合作用下的自发收缩现象,发现第二类哑铃畴的自发收缩不仅与面内场的大小有关,而且还与第二类哑铃畴在面内场中所处方向有关.采用照相法形象地揭示出:当第二类哑铃畴与面内场垂直时最容易发生自发收缩;当第二类哑铃畴与面内场平行时最难发生自发收缩.实验还证明了第二类哑铃畴在自发收缩过程中存在垂直布洛赫线的丢失现象.  相似文献   

2.
垂直布洛赫线在畴段畴壁中的形成和消失   总被引:1,自引:0,他引:1       下载免费PDF全文
在不同的直流偏场下,对脉冲偏场作用后的磁泡膜中的磁畴观测结果表明:磁泡膨胀时的分枝生长往往伴随有大量垂直布洛赫线(以下称VBL)产生;它的正负与反向畴膨胀时所施加的直流偏场大小有确定关系;在幅度不太高的系列脉冲作用下畴端运动可使畴壁中形成大量VBL;足够强的脉冲偏场可使VBL消失。 关键词:  相似文献   

3.
三类硬磁畴的形成及静态特性   总被引:8,自引:0,他引:8       下载免费PDF全文
本文提出畴壁中含有大量VBL的石榴石磁泡材料的三类硬磁畴的分类标准,描述了它们的形成方法和静态特性,并示出典型照片。从形成条件可以合理地推论,畴壁中VBL数目的增加导致硬磁畴静态特性的质的变化。 关键词:  相似文献   

4.
李丹  郑德娟  周雁  韩宝善 《物理学报》1999,48(13):250-256
对于石榴石磁泡薄膜,提出了产生单个枝状畴(MBD)的“低静态偏磁场法”.MBD的形成是与其畴壁内垂直布洛赫线(VBL)的形核相联系的.随着静态偏磁场Hb从“枝状膨胀的临界偏磁场”H[d]的降低,相应的MBD的畴形变得越来越复杂,伴随有几类硬磁泡的相继形成.对MBD进行了分形研究,把线结构维数的计算应用于MBD极其弯曲的畴壁结构,定量地描述了它们的弯曲和分枝程度,并与其畴壁内VBL的形核联系起来. 关键词:  相似文献   

5.
研究石榴石磁泡膜中硬磁畴畴壁中垂直布洛赫线的稳定性可为研制布洛赫线存储器提供有益的帮助 .3类硬磁畴的形成是研究硬磁畴稳定性的前提 .本文综述了在石榴石磁泡膜上形成硬磁畴的 2类方法———“脉冲偏场法”和“低直流偏场法” .结合文献中的典型样品 ,对用“脉冲偏场法”和“低直流偏场法”形成 3类硬磁畴的过程进行了简单介绍 .  相似文献   

6.
霍素国  聂向富  韩宝善 《物理学报》1991,40(12):2012-2017
实验研究面内场Hin和静态偏磁场Hb作用下,(111)面磁泡膜内条畴的消失过程。保持Hb恒定,增加Hin,测量条畴消失场Hs*和泡畴消失场Hk*与面内场方向β的变化关系。计及立方磁晶各向异性的影响,建立Hin和Hb共同存在时的条畴稳定性理论。定性解释了实验的主要特点。导出黑、白条畴同时消失时的角度 βn=1/3(2nπ±arc cos│3/(21/2)(MsHb)/K1│)(n=0,±1,±2,…)与实验基本符合。 关键词:  相似文献   

7.
温度对普通硬磁泡的影响   总被引:5,自引:0,他引:5       下载免费PDF全文
霍素国  聂向富  韩宝善 《物理学报》1988,37(10):1703-1706
实验研究了温度对外延石榴石磁泡薄膜中硬磁泡及其相应硬条畴的影响。发现了一个与材料参量有关的临界温度T0当试验温度T0时,硬条畴畴壁中的VBL链在升降温后不变;而当T>T0时,VBL链消失,所有硬磁泡都软化为正常磁泡。当畴壁中的VBL处于压缩态时,较硬的硬磁泡在较低的温度下软化。软化时,VBL消失的方式是整个VBL链的解体。 关键词:  相似文献   

8.
当面内磁场大于某一阈值Hin′时,硬磁泡和硬畴段将变为正常泡和段。我们测量了不同磁泡材料的Hin′。随垂直于膜面直流偏磁场的增大,Hin′减小。观察到这种转变是一种弛豫过程,在适当条件下可以持续数秒或数十秒。采用Slonczewski和Malozemoff提出的面内场布洛赫点形核的概念对得到的实验结果做了定性的解释。 关键词:  相似文献   

9.
脉冲偏场作用下石榴石磁泡薄膜中布洛赫线的形成   总被引:4,自引:0,他引:4       下载免费PDF全文
Hu Yun-Zhi  孙会元 《物理学报》2008,57(8):5256-5260
实验研究了石榴石磁泡薄膜中不同脉冲宽度下产生的硬磁畴的动态特性.结果表明:由零偏场下产生的枝状畴收缩而成的哑铃畴均逆时针转动,与产生枝状畴时所用的脉冲偏场的脉冲宽度无关.而固定直流偏场下由软畴段硬化而成的哑铃畴的转动状态,则与所用的硬化脉冲偏场的脉冲宽度有关.低脉冲宽度下硬化成的哑铃畴均逆时针转动,随硬化脉冲宽度的升高,出现混合转动向顺时针转动的过渡.由此揭示了直流偏场和脉冲偏场在石榴石磁泡薄膜中形成正、负垂直布洛赫线的作用. 关键词: 磁畴 磁泡 垂直布洛赫线  相似文献   

10.
在八个(111)面磁泡膜上,观察了施加面内(in-plane)磁场后在不同晶轴方向上条状畴的消失过程,测量了条畴消失场Hs*和磁畴消失场Hk*与面内磁场的方向的关系。本文计及立方磁晶各向异性,完善了面内磁场中条畴的稳定性理论。用该理论定性地解释了实验结果的主要特点。导出了Hs*与立方各向异性及面内场方向的两种近似的理论关系,它们分别适用于面内场方向靠近和不十分靠近〈110〉晶轴的情形。它们和实验结果是大致符合的。在〈110〉晶轴上,理论关系具有下列简单的形式:Hk*<110>=Hs*<110>=Hk{1+(k1/2Ku)-[al/h(4πMs/Hk)2]2/3},此式与实验结果符合得相当好。 关键词:  相似文献   

11.
12.
霍素国  韩宝善  李伯臧 《物理学报》1994,43(8):1360-1364
实验研究了温度对液相外延石榴石磁泡薄膜中条状普通硬磁畴壁内的垂直布洛赫线(VBL)链解体临界面内磁场区间的影响。发现存在一对特征温度T(1)0 和 T(2)0(前者比后者略低但均高于室温),在从室温到T(2)0的每个温度T下,使VBL逐渐消失的面内磁场Hip都分布于一个与T有关的区间[Hip(1)(T), Hip(2)(T)]内,称为临界面内磁场区间:Hip<Hip(1)(T)时,VBL链保持不变;Hip(1)(T)< Hip < Hip(2)(T)时,随着Hip的增加,越来越多的VBL消失;Hip > Hip(2)(T)时,所有VBL都消失。Hip(1)(T),Hip(2)(T)及Hip(2)(T)-Hip(1)(T)均随T的升高而下降,前二者分别于T(1)0 和 T(2)0降为零。比值Hip(2)(T)/Hip(1)(T)随T的升高而升高,在低温段(包括室温)升高缓慢且约为21/2,在T(1)0附近急剧升高且至T(1)0时趋于∞。对以上结果做了理论分析。 关键词:  相似文献   

13.
王远飞  韩宝善 《中国物理》1999,8(7):539-544
Experiments were statistically carried out on the behavior of vertical-Bloch-line(VBL) chains in the walls of the second kind of dumbbell domains (IIDs) is garnet bubble films subjected to joint action of static bias field Hb and in-plane field Hip. The curves of the four critical in-plane fields, (Hip)IID-ID (Hip)IID-OHB (Hip)IID-SB and H'ip vs Hb were measured and explained. In particular, in terms of two series of IID photos, a new experimental manifestation of the unknown "number effect" of VBL chains was found.  相似文献   

14.
实验研究了面内磁场对一次脉冲偏磁场作用下外延石榴石薄膜中硬磁泡形成的影响,发现存在一个使硬磁泡不再形成的临界面内磁场Hin0,它与材料参量有关,通过实验,运用面内磁场对条状畴的作用和枝状畴的形成,定性解释了软硬磁泡形成的分界场H[b]随面内磁场增大、快降以及缓降这三个物理过程。 关键词:  相似文献   

15.
The stability of vertical Bloch line (VBL) chains was statistically studied for all three types of bard domains in garnet bubble films subjected to an in-plane field Hip. With a set of integrate data taken from seven bubble samples and with two typical figures of a sample, four main features of the behavior of VBL chains subjected to Hip were summarized.  相似文献   

16.
A theory describing the magnetic properties of a two-band superconductor with a varying charge carrier density is constructed. The upper critical field H c2(ab) parallel to the ab plane and field H c2(c) parallel to the c axis are determined in the entire temperature range 0 < T < T c . A considerable increase in upper critical field H c2(ab) as compared to H c2(c) because of strong anisotropy of the system is detected. Anisotropy of coefficient γ H = H c2(ab) / H c2(c) is obtained as a function of temperature for pure MgB2 and as a function of the chemical potential in the case when Mg and B atoms are replaced with other chemical elements. A correlation between the variation in the superconducting transition temperature upon an increase in the chemical potential and critical magnetic fields H c2(ab) and H c2(c) is observed. The effect of doping on magnetic anisotropy is also determined.  相似文献   

17.
The results of experimental studies on hysteresis in magnetization, thermomagnetic history effects, anomalous variations in magnetic hysteresis curves and the decay rates of magnetization obtained under different thermomagnetic histories in specimens of conventional and high temperature superconductors are presented. The Bean’s critical state model is considered adequate to explain magnetic behaviour in conventional hard superconductors. The similarity in the general features of the results of different experiments on specimens of the two families of superconductors underscores the efficacy of the said model to understand some aspects of the macroscopic magnetic response of high temperature superconductors as well. For instance, the isothermal magnetization hysteresis loop which comprises of magnetization curves along forward (−H max to +H max) and reverse (+H max to −H max) paths define an envelop within which all isothermal magnetization data along different thermomagnetic histories lie. There exist inequality relationship between various field values identified asH peak,H I,H II etc. in isothermal magnetization hysteresis as well as magnetic relaxation data. The entire field span of an isothermal magnetization hysteresis data set can be considered to comprise of three parts corresponding to (M rem(H)−M FC(H)+M ZFC(H)) being equal to, less than or greater than zero, whereM rem(H) are the remanent magnetization values obtained on reducing field to zero after having the specimen in different applied field (H) values. There are, however some situations amongst thermomagnetic history effects in specimens which show incomplete flux trapping on field cooling, where the critical state model has been found inadequate.  相似文献   

18.
The lower critical field H c1 cyl (T) of a superconducting cylinder with radius r 0ξ(T)≪λ(T) is found on the basis of the Ginzburg-Landau theory with various boundary conditions. These results together with the well-known results for the upper critical field are used to construct phase diagrams in terms of the field versus the reduced radius r 0ξ(T) variables. The jump in the average magnetization at H c1 cyl (T) is calculated as a function of the reduced radius. Pis’ma Zh. éksp. Teor. Fiz. 69, No. 8, 537–542 (25 April 1999)  相似文献   

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