熔体抽拉非晶微丝磁畴调控及其与GMI效应相关性

发布时间：2018-05-24 01:53

本文选题：熔体抽拉 + 非晶微丝　；参考：《哈尔滨工业大学》2015年博士论文

【摘要】：本文分别从应力作用、电化学方式处理、直流焦耳热与梯度退火、液态介质焦耳退火、直流与抛光复合式退火处理对微丝进行磁畴结构调制,并系统研究了磁畴结构与巨磁阻抗(GMI)效应对应关系,由此探讨两者的相关性。拉伸应力可有效的改善微丝周向畴结构,使周向各向异性场变大。拉伸应力203.7MPa时,阻抗达到最大比值[?Z/Z]max(%)=223.6%,相对制备态时提高了22.7%;扭转应力产生扭矩,感生螺旋各向异性,其周向分量有助于周向各项异性场、畴结构的改善与周向磁导率的提高,有助于GMI的改善;频率在f=15MHz、扭转应变?=20.4(2?rad/m)时,[?Z/Z%]max(%)达到最大值194.4%;磁畴变为“Z字型”弯曲畴;平均畴尺寸1.1?m。电镀能改变微丝表面磁各向异性,从而对GMI性能产生影响。等间距环向电镀Ni(镀层宽度2mm)3节后?Z/Zmax(%)=251.1%,比制备态高出40.4%;电镀后,微丝未镀区域周向畴的畴壁更清晰,平均畴尺寸0.73?m;Ni镀层厚度约3?m,迷宫状畴与整体畴取向周向分布;螺旋微电镀Ni时,当螺旋间距为50~200?m,?Z/Zmax(%)比值相对制备态有所提高;Ni层畴呈迷宫状畴分布,畴壁不清晰;微丝表面周向畴分布明显,平均畴尺寸为0.83?m。采用阶梯式焦耳热退火处理后,阻抗制备态比值?Z/Zmax(%)=469.6%;在阶梯式80m A退火后,交流频率f=7.4MHz,获得了更高的GMI比值:?Z/Zmax(%)=654.1%(H0Oe);?Z/Zmax(%)=650.2%(H0Oe)。100m A阶梯式焦耳退火后的?Z/Zmax(%)比值仍然很高,达到了631.9%(H0Oe)与624.6%(H0Oe),具有较大的响应量程-1.5~0Oe/0~1.5Oe;对应的场响应灵敏度分别为:?=401.0%/Oe与?=397.5%/Oe。退火后,畴结构得到改善,100m A阶梯式电流退火后磁畴平滑且周向畴分布增多,交错畴出现,平均畴宽度增至0.98?m。由于GMI性能源于微丝的趋肤效应,通过在液氮中焦耳热退火,加大退火电流到300m A电流幅值后,实现了微丝“芯部”晶化,而表面“壳层”仍为非晶态的“芯—壳”微结构。这种结构源于液氮低温作用避免微丝壳层晶化,此时壳层厚度约为100nm。在频率为8.1MHz时,GMI比值达到425%;外场在2.5~6.5Oe区间,响应灵敏度达到99.4%/Oe;200m A电流幅值退火后,频率在4~12MHz之间,GMI曲线呈现出0~6Oe的单调递增响应与10~80Oe的严格线性响应;后者较大的线性响应特性,可用于检测生物磁传感器与探测理疗产品的漏磁场;由此也验证了微丝GMI性能取决于表面性能。当采用300m A电流幅值退火后,由MFM获得表面为周向与迷宫状组成的复合畴结构,周向畴明显改善,有序度提高,清晰的周向畴平均宽度为0.76?m。分析了Co基非晶微丝磁畴结构的形成机理,并探明了熔体抽拉Co-Fe基非晶微丝的磁畴结构,提出了熔体抽拉Co-Fe基非晶微丝具有高的GMI比值与响应灵敏度的磁畴结构的三个特征:(a)单一周向畴,畴反向交替,规则分布;无杂散畴与“毛刺”现象;(b)周向畴界清晰且圆整,畴宽度均匀,尺寸约为1?m;(c)畴壁为180°Bloch壁,畴壁清晰,周向完整,畴壁平均宽度约10nm;无畴壁钉扎现象。
[Abstract]:In this paper, the magnetic domain structure is modulated from the stress action, the electrochemical treatment, the DC Joule heat and the gradient annealing, the Joule annealing of the liquid medium, the direct current and the polished annealing treatment. The correlation between the magnetic domain structure and the giant magnetic impedance (GMI) effect is studied systematically, and the correlation between the two is discussed. The tensile stress can be effective. In order to improve the circumferential domain structure, the circumferential anisotropy field becomes larger. When the tensile stress is 203.7MPa, the maximum ratio [? Z/Z]max (%) =223.6%) increases by 22.7% relative to the preparation state; torsional stress produces torque, and the spiral anisotropy is generated, and its circumferential component is helpful to the circumferential heterosexual fields, the improvement of the domain structure and the peri permeability. Improvement is helpful to the improvement of GMI; when the frequency is f=15MHz, the torsional strain? =20.4 (2? Rad/m), [? Z/Z%]max (%)] reaches the maximum value of 194.4%; the magnetic domain becomes the "Z type" curved domain; the average domain size 1.1? M. electroplating can change the magnetic anisotropy of the microfilament surface, thus affecting the GMI performance. The equidistance ring to the electroplating Ni (2mm) 3 of electroplating (2mm) 3? Z/Zmax (%) =251.1% is 40.4% higher than that of preparation state; after electroplating, the domain wall of the circumferential domain is clearer and the average domain size is 0.73? M; the thickness of the Ni coating is about 3? M, the labyrinth domain and the whole domain orientation are circumferential; when the spiral microelectroplating Ni, the ratio of the spiral spacing to 50~200? M, Z/Zmax (%) is relative to the prepared state; the Ni layer domain is labyrinth domain distribution. The wall is not clear; the surface of the microfilament is obviously distributed on the surface, and the average domain size is 0.83? M. using the step Joule annealing treatment. The impedance prepared state ratio? Z/Zmax (%) =469.6%; after the step 80m A annealing, the AC frequency f=7.4MHz is obtained. The higher GMI ratio is obtained: Z/ Zmax (%) =654.1% (H0Oe); Z/Zmax (%) Z/Zmax (%) stepped Joule retreat. The ratio of Z/Zmax (%) after fire is still high, reaching 631.9% (H0Oe) and 624.6% (H0Oe) and having a larger response range -1.5~0Oe/0~1.5Oe. The corresponding field response sensitivity is: after annealing of =401.0%/Oe and =397.5%/Oe., the domain structure is improved, and the 100m A step type current is smooth and the distribution of the peripheral domain is increased after the 100m A ladder type current annealing, and the interlaced domains appear. The average domain width increased to 0.98? M., due to the skin effect of GMI energy in microfilament, through the Joule heat annealing in liquid nitrogen, increasing the annealing current to the 300m A current amplitude, the "core" crystallization of the microfilament was realized, while the surface "shell" was still a amorphous "core shell" microstructure. This structure was derived from the effect of liquid nitrogen at low temperature to avoid microfilament shell. Layer crystallization, when the shell thickness is about 100nm. at 8.1MHz, the GMI ratio reaches 425%; the external field is in the 2.5~6.5Oe interval, the response sensitivity is 99.4%/Oe; after the 200m A current amplitude is annealed, the frequency is between 4~12MHz and the GMI curve shows the strict linear response of 0~6Oe and the 10~ 80Oe; the latter has a larger linear response characteristic, It can be used to detect the leakage magnetic field of the biological magnetic sensor and the detection of the physiotherapy products. It is also proved that the performance of the microfilament GMI depends on the surface performance. When the 300m A current amplitude is annealed, the composite domain structure with the circumferential direction and the labyrinth shape is obtained by the MFM. The circumferential domain is obviously improved, the order degree is improved, and the clear circumferential domain average width is 0.76? M. analyzed the formation mechanism of the magnetic domain structure of Co base amorphous microfilament, and explored the magnetic domain structure of melt pulling Co-Fe base amorphous microfilament, and proposed three characteristics of magnetic domain structure with high GMI ratio and response sensitivity of melt pulling Co-Fe base amorphous microfilaments: (a) single week domain, domain reverse alternation, regular distribution; no stray domain and "burr" "The phenomenon; (b) circumference is clear and round, the domain width is uniform, the size is about 1? M; the (c) domain wall is 180 degree Bloch wall, the domain wall is clear, the circumferential direction is complete, the domain wall average width is about 10nm; no domain wall pinning phenomenon.
【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB303

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