Effect of annealing on the electrical and magnetic properties of electrodeposited Ni and permalloy nanowires
Effect of annealing on the electrical and magnetic properties of electrodeposited Ni and permalloy nanowires
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DOI：
10.1016/j.jmmm.2019.166276
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发表时间：
2020-04
影响因子：
2.7
通讯作者：
R. Dost;Y. Zhou;Hongzhou Zhang;D. Allwood;B. Inkson
中科院分区：
文献类型：
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作者：
R. Dost;Y. Zhou;Hongzhou Zhang;D. Allwood;B. Inkson
研究了退火对圆柱形镍基纳米线微观结构和电、磁性能的影响。采用电化学沉积的方法，分别在聚碳酸酯和阳极氧化铝纳米孔模板上制备了直径为~275 nm的镍纳米线和直径为~70 nm的坡莫合金纳米线。对生长和高达650℃热处理的纳米线进行了表征。透射电子显微镜成像和衍射结果显示，纳米线的晶粒生长与温度相关，最初为<8 nm （Ni）和<20 nm （Py）晶粒的纳米晶结构（未经处理），热处理后晶粒达到~160 nm （Ni）和~70 nm (Py)，晶粒的多结晶度较粗，后者受到纳米线宽度的限制。用扫描电镜原位测量了生长态和650℃退火镍纳米线的电导率。在低电流密度下，退火纳米线的导电性估计是生长纳米线的两倍。我们把这种增长归因于观察到的晶粒生长。退火后的纳米线随后受到不断增加的电流密度的影响。在120 kA.mm−2以上，纳米线电阻开始上升。在450ka .mm−2时，纳米线熔化，电流停止流动。对生长和退火后的纳米线阵列进行了磁强计分析，结果表明纳米线阵列具有准薄膜的磁性。退火金属丝的矫顽力和饱和场呈负相关，在200°C的温度下，矫顽力和饱和场的可调性达到25%。
The influence of annealing on the microstructure and the electrical and magnetic properties of cylindrical nickel-based nanowires has been investigated. Nanowires of nickel of ~275 nm diameter and of permalloy (Py) of ~70 nm diameter were fabricated by electrochemical deposition into nanoporous templates of polycarbonate and anodic alumina, respectively. Characterization was carried out on as-grown and up to 650 °C heat-treated nanowires. Transmission electron microscopy imaging and diffraction of the nanowires showed a temperature-correlated grain growth of an initially nanocrystalline structure (untreated) with <8 nm (Ni) and <20 nm (Py) grains towards coarser poly-crystallinity after heat treatment with grains up to ~160 nm (Ni) and ~70 nm (Py), the latter being limited by the nanowire width. The electrical conductivity of individual as-grown and 650 °C annealed Ni nanowires was measured in-situ by scanning electron microscopy. At low current densities, the conductivity of annealed nanowires was estimated to have doubled over as-grown nanowires. We attribute this increase to the observed grain growth. The annealed nanowire was subsequently subjected to increasing current densities. Above 120 kA.mm−2the nanowire resistance started to rise. At 450 kA.mm−2, the nanowire melted and current flow ceased. Magnetometry of as-grown and annealed nanowire arrays showed them to display quasi-thin film magnetic properties. Coercivity and saturation field were inversely correlated in annealed wires and a 25% tunability in these properties was achieved at just 200 °C.