• Current Applied Physics
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• v.18 no.11
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• pp.1240-1247
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• 2018

Magnetic hysteresis in Ni nanowire arrays grown by electrodeposition inside the pores of anodic alumina templates is studied as a function of temperature in the range between 5 K and 300 K. Nanowires with different diameters, aspect ratios, inter-wire distance in the array and surface condition (smooth and rough) are synthesized. These microstructure parameters are linked to the different free magnetic energy contributions determining coercivity and the controlling magnetization reversal mechanisms. Coercivity increases with temperature in arrays of nanowires with rough surfaces and small diameters -33 nm and 65 nm- when measured without removing the alumina template and/or the Al substrate. For thicker wires -200 nm in diameter and relatively smooth surfaces- measured without the Al substrate, coercivity decreases as temperature rises. These temperature dependences of magnetic hysteresis are described in terms of an effective magnetic anisotropy $K_a$, resulting from the interplay of magnetocrystalline, magnetoelastic and shape anisotropies, together with the magnetostatic interaction energy density between nanowires in the array. The experimentally determined coercive fields are compared with results of micromagnetic calculations, performed considering the magnetization reversal mode acting in each studied array and microstructure parameters. A method is proposed to roughly estimate the value of $K_a$ experimentally, from the hysteresis loops measured at different temperatures. These measured values are in agreement with theoretical calculations. The observed temperature dependence of coercivity does not arise from an intrinsic property of pure Ni but from the nanowires surface roughness and the way the array is measured, with or without the alumina template and/or the aluminum support.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.830-833
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• 2002

최근 나노 구조 (nano structure)를 만들기 위한 시도 중 하나로서 스스로 조직화(self organization)하여 나노 구조를 형성하는 물질을 나노 소자 제작을 위한 형틀 (template)로 이용하려는 시도가 활발히 진행되고 있다. 이러한 물질로서 주목을 받고있는 것 중 하나가 전해질 용액에서 알루미늄을 양극산화(anodization) 시켰을 때 형성되는 다공성 알루미나 박막이다. 본 연구에서는 고 순도 알루미늄을 기계적으로 연마(mechanical polishing)하고 공기 분위기에서 어닐링 (annealing)하여 알루미늄을 재결정화(recrystallization) 시키고 인가 전압이 40 V인 정 전압하에서 0.3 M의 수산(oxalic acid)을 전해질로 사용하면서 양극산화를 수행하여 평균 직경이 65 nm인 고도로 배열된 육방밀집구조의 나노 다공성 박막을 제작하였다. 또한 같은 방향의 육방밀집 배열은 크기가 수 ${\mu}m$인 영역(grain)을 형성하고 있었으며, 평균적인 pore의 밀도는 $1.1{\times}10^{10}/cm^2$였다.

• Bulletin of the Korean Chemical Society
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• v.29 no.4
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• pp.758-760
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• 2008

Nanoporous AAO (Anodic Aluminum Oxide) membranes have many advantages as a template for variety of magnetic materials. Materials can be embedded into the pores by electrodeposition, sputtering or magnetic-field-assisted infiltration of magnetic nanoparticles. This work focuses on the fabrication of the magnetic structures in the AAO templates by electrodeposition. Our method allows the controlled growth of Co nanostructures within the porous alumina membrane in the form of dots, rods and long wires. The shape of Co nanostructures has been investigated by field emission scanning electron microscope (FESEM). The magnetic hysteresis loops of Co nanostructures were measured using SQUID at 5 K and 300 K. The magnetic properties of the Co nanostructures are proportional to their aspect ratios and can be controlled by changing the aspect ratios.

• Korean Chemical Engineering Research
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• v.52 no.2
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• pp.205-208
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• 2014

Here, we reported mass-produced organic nanowires with uniform sizes based on poly(9,9-dioctylflurorene) (PFO), poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT), (regioregular poly(3-hexylthiophene) (P3HT) which are well known as organic semiconductors for opto/electronics applications, using a melt-assisted wetting method with anodic alumina membrane. The conjugated polymer nanowires showed uniformed diameters (D=250~300 nm) and lengths ($L={\sim}30{\mu}m$) with defect free smooth surface regardless of a kinds of semiconductors. In addition, the nanowires were uniformly deposited onto glass substrates by spray-coating method. Under the UV light irradiation, PFO and F8BT nanowires showed blue and yellow emissions, respectively.