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Ga 극초박막의 계면특성과 초전도 물성제어에 대한 연구
이년종(Nyun Jong Lee),김태희(Tae Hee Kim) 한국자기학회 2010 韓國磁氣學會誌 Vol.20 No.6
Spin polarized tunneling studies were carried out with Al-Ga bilayer as a spin detector, by Meservey-Tedrow technique. The superconductor (SC)/Insulator (I)/Ferromagnet (FM) tunnel junctions were provided by ultra high vacuum molecular beam epitaxy (UHV-MBE) technique. The analysis of interfacial properties in the Al-Ga bilayer was also carried out by Auger electron spectroscopy. It was observed that the superconducting transition temperature and energy gap were raised in comparison with that of bulk Ga and pure ultrathin Al films. Current studies clearly show how one can modify the material properties at the interface just with a few monolayers.
장은영(Eun Young Jang),이년종(Nyun Jong Lee),최등장(Deung Jang Choi),김태희(Tae Hee Kim) 한국자기학회 2008 韓國磁氣學會誌 Vol.18 No.4
Magnetite (Fe3O4) is currently one of key materials for applications in magnetic storage and many bioinspired applications because bulk Fe₃O₄ has a high Curie temperature (Tc = ~850 K) and nearly full spin polarization at room temperature (RT). In this work, Fe₃O₄ nanoparticles with different sizes of 12 to 15 ㎚ were prepared in a well-controlled manner by a nonhydrolytic synthetic method. Here, we report the significant intergrain magneto-resistance (MR) of ~2 % at RT in Fe₃O₄ nanoparticle pellets. The tunneling conductance was also investigated based on the Brinkman model, as well. Our results show clearly that the surface or interfacial property of the particles plays a crucial role in the MR effect.
Cu-Phthalocyanine 유기장벽 두께에 따른 스핀소자의 전기적 특성 변화 양상
배유정(Yu Jeong Bae,),이년종(Nyun Jong Lee),김태희(Tae Hee Kim) 한국자기학회 2012 韓國磁氣學會誌 Vol.22 No.5
V-I characteristics of Fe(100)/MgO(100)/Cu-phthalocyanine (CuPc)/Co hybrid magnetic tunnel junctions were investigated at different temperatures. Fe(100) and Co ferromagnetic layers were separated by an organic-inorganic hybrid barrier consisting of different thickness of CuPc thin film grown on a 2 nm thick epitaxial MgO(100) layer. As the CuPc thickness increases from 0 to 10 nm, a bistable switching behavior due to strong charging effects was observed, while a very large magenetoresistance was shown at 77 K for the junctions without the CuPc barrier. This switching behavior decreases with the increase in temperature, and finally disappears beyond 240 K. In this work, high-potential future applications of the MgO(100)/CuPc bilayer were discussed for hybrid spintronic devices as well as polymer random access memories (PoRAMs).
RF-스퍼터링 기법으로 제작한 Fe<SUB>3</SUB>O<SUB>4</SUB> 박막에 Ta 기저층이 미치는 효과
국지현(Jihyeon Gook),이년종(Nyun Jong Lee),배유정(Yu Jeong Bae),김태희(Tae Hee Kim) 한국자기학회 2015 韓國磁氣學會誌 Vol.25 No.2
Si(100)\200 nm SiO<SUB>2</SUB>\5 nm Ta\5 nm MgO\35 nm Fe<SUB>3</SUB>O<SUB>4</SUB> multi-layers were prepared by using RF-sputtering and ultra-high vacuum molecular beam epitaxy (UHV-MBE) techniques. After post-annealing the multi-layers at 500℃ for 1 hour under the high vacuum of~1 × 10<SUP>?6</SUP> Torr, we observed ferromagnetic properties at room temperature as well as the Verwey transition which is the typical features of magnetite crystals formed. We have carried out a comparative study of the effect of Ta buffered layer on the crystallinity and magnetic properties of Fe<SUB>3</SUB>O<SUB>4</SUB> thin films prepared under different growth and annealing conditions.
Fe\MgO\Cu-Phthalocyanine 복합구조 계면구조와 그 전자기적 특성
배유정(Yu Jeong Bae),이년종(Nyun Jong Lee),김태희(Tae Hee Kim),Andrew Pratt 한국자기학회 2013 韓國磁氣學會誌 Vol.23 No.6
The influence of insertion of an ultra-thin Cu-Phthalocyanine (CuPc) between MgO barrier and ferromagnetic layer in magnetic tunnel juctions (MTJs) was investigated. In order to understand the relation between the electronic and structural properties of Fe\MgO\CuPc, the surface (or interface) analysis was carried out systematically by using spin polarized metastable He de-excited spectroscopy for the CuPc films grown on the Si(001)\5 nm MgO(001)\7 nm Fe(001)\1.6 nm MgO(001) multilayer structure as the thickness of CuPc increases from 0 to 5 nm. In particular, for the 1.6 nm CuPc surface, a rather strong spin asymmetry between upand down-spin band appears while it becomes weaker or disappears for the CuPc films thinner or thicker than ~1.6 nm. Our results emphasize the importance of the interfacial electronic properties of organic layers in the spin transport of the hybrid MTJs.
최등장(Deung Jang Choi),장은영(Eun Young Jang),이년종(Nyun Jong Lee),김태희(Tae Hee Kim) 한국자기학회 2007 韓國磁氣學會誌 Vol.17 No.5
Understanding the spin polarization (P) has been an ongoing research challenge. The Co<SUB>1 ? x</SUB>Mn<SUB>x</SUB> (x = 0.27, 1) and Co<SUB>1 ? x</SUB>Fe<SUB>x</SUB> (x = 0, 0.5, 1) films were prepared using UHV-MBE system. For these films, the magnetic properties and spin polarization were investigated using SQUID and Meservey-Tedrow technique, respectively. Although measured P is uncorrelated to the bulk magnetic moment (M) in Co-Fe and Ni-Fe alloy films, it correlates with M in some alloys such as Co-Mn and Ni-Cu. The results can be understood by the tunneling currents made up of the hybridized sp-d electrons near the Fermi-energy level. Our work shows the feasibility to tailor new materials with large P values.