• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.61-64
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• 2000

$^{11}$B NMR measurements have been performed to investigate local electronic structure and 4f spin dynamics for TbNi$_2$B$_2$C single crystal. $^{11}$B NMR spectra show three resonance peaks due to the quadrupolar interaction. Shift and linewidth are huge and strongly temperature-dependent. In addition, both are proportional to magnetic susceptibility, indicating that the hyperfine field at the boron site originates from the 4f spins of Tb. $^{11}$B NMR shift and relaxation rates show high anisotropy for field parallel and perpendicular to the c-axis. Anisotropy of the shift and the relaxation rates suggests that the hyperfine field perpendicular to the c-axis is larger.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.206-209
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• 1999

Magnetic and superconducting properties in a series of intermetallic compounds Y$_{1-x}Tb_xNi_2B_2C$ were investigated by measuring the temperature dependent magnetization, M (T), and resitivity, ${\rho}$ (T). As Tb concentration, x, is increased, the superconducting transition temperature, T$_c$, decreases and eventually disappears in the vicinity of x = 0.5 while Neel temperature, T$_N$, appears abruptly near x = 0.4 and increases linearly. Of particular interest is the collision of superconductivity and antiferromagnetism around x = 0.4. The linear decrease of T$_c$ for dilute Tb concentration seems to follow the Abrikosov-Gor'kov behavior, while the decay of T$_c$ below T$_c$ is expected to originate from the effective magnetic field on the conduction electrons. The Ginzburg-Landau theory was phenomenologically constructed to explain this competition of superconducting order parameter and antiferromagnetic order parameter with the multi-band model.

• Journal of Magnetics
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• 제1권2호
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• pp.64-68
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• 1996

Compared with the conventional magnetostriction in Ni alloys which are in the order of several tens ppm (Parts Per Million =10-6), RFe$_2$(R = rare earth element) Laves Phase intermetallic compounds show large saturation magnetostriction in the range of a few thousands ppm. However, the large external magnetic field necessary to obtain saturatio magnetostriction has due to large magnetocrystalline anisotropy energy restrained the applicationof magnetostriction materials in RFe$_2$intermetallic compounds. As a result of its solution, the largest published value of effective giant magnetostriction in a low external magnetic field (less than a few hundred Oe) is reported in this paper by means of amorphisation of RFe$_2$intermetallic compounds with the addition of boron, as a half metal. For the amorphous (SmFe$_2$)0.97 B0.03 alloys, the effective magnetostriction of -545 and -610 $\times$ 10-6 is obtained at 400 and 1,000 Ie, respectively. Moreover, the effective magnetostriction of 590 and 630$\times$10-6 in the amorphous (TbFe$_2$)0.98 B0.02 alloys is also found at 400 and 1,000 Oe, respectively. This result will provide a clue to understanding the effect of half metal on anomalous increase of the effective giant magnetostriction and attract the great attention for magnetostriction applications.

• Journal of Magnetics
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• 제16권2호
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• pp.83-87
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• 2011

The vortex-driven magnetization process of micron-sized, exchange-coupled square elements with composition of $Ni_{80}Fe_{20}$ (12 nm)/$Ir_{20}Mn_{80}$ (5 nm) is investigated. The exchange-bias is introduced by field-cooling through the blocking temperature (TB) of the system, whereby Landau-shaped vortex states of the $Ni_{80}Fe_{20}$ layer are imprinted into the $Ir_{20}Mn_{80}$. In the case of zero-field cooling, the exchange-coupling at the ferromagnetic/antiferromagnetic interface significantly enhances the vortex stability by increasing the nucleation and annihilation fields, while reducing coercivity and remanence. For the field-cooled elements, the hysteresis loops are shifted along the cooling field axis. The loop shift is attributed to the imprinting of displaced vortex state of $Ni_{80}Fe_{20}$ into $Ir_{20}Mn_{80}$, which leads to asymmetric effective local pinning fields at the interface. The asymmetry of the hysteresis loop and the strength of the exchange-bias field can be tuned by varying the strength of cooling field. Micromagnetic modeling reproduces the experimentally observed vortex-driven magnetization process if the local pinning fields induced by exchange-coupling of the ferromagnetic and antiferromagnetic layers are taken into account.

• 한국제4기학회지
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• 제16권1호
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• pp.1-16
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• 2002

황해 중앙부 해역에 분포하는 니토대의 공급지와 퇴적작용을 파악할 목적으로 이곳 니질 퇴적물에서 채취한 4개의 시료에서 분석한 화학조성과 기존의 황하, 양자강 및 한반도의 금강 퇴적물 등의 지화학적 자료와 비교하고 퇴적률을 추정하였다. 연구지역 표층 퇴적상의 분포는 사질 퇴적상이 분포하는 동쪽지역, 니토대가 분포하는 서쪽지역, 중앙부지역에 남북방향의 대상분포를 보이는 혼합 퇴적상으로 구분된다. 퇴적물내 탄산염 함량은 2.B~10.5%의 범위를 보이고 사질 퇴적물이 분포하는 동쪽보다 니질 퇴적물이 분포하는 서쪽으로 갈수록 점차 증가하는 경향을 보인다 Pb-210 동위원소를 이용한 연구지역 니질 퇴적물의 퇴적률은 0.21~0.68cm/yr 혹은 0.176~0.714 g/$\textrm{cm}^2$.yr의 범위를 보였다. 황하와 가까운 산둥반도 동쪽 정점 CY96010에서 퇴적률은 0.68cm/yr 혹은 0.714g/$\textrm{cm}^2$. yr의 높은 값을 보이고, 황해 중앙부 해역 정점 CY96008과 CY96002에서 퇴적률은 0.21~0.23cm/yr혹은 0.176~0.220g/$\textrm{cm}^2$. yr로 낮은 값을 보여 황하기원 퇴적물이 황해 중앙부 해역까지 이동되어 퇴적되고 있음을 의미한다. 황해 중앙부 해역 니질 퇴적물의 화학조성 중 Ca, Na, Sr, Ho, La, Tb 및 Ta원소함량과 Ca/Ti비는 양자강 퇴적물보다는 높고, 황하보다는 낮거나 이와 비슷한 함량 변화 경향을 보였고, Fe, Ti, Ni, Co, Cr, Cu, Pb, Sc, Ce, Nd, Sm, Eu, Gd 및 Dy 원소함량은 황하 퇴적물 보다는 높고, 양자강보다는 낮으나 이와 비슷한 함량변화를 보였다. 반면, Mn, K 및 Sr 원소는 금강과 황해 동쪽의 퇴적물보다는 낮으나 이와 비슷한 함유량을 보였고, Zn, Rb, Cd, U, Cs 및 Li 원소는 비교지역 보다 높은 함량치를 보였다. 따라서 황해 중앙부 해역에 분포하는 니질 퇴적물의 공급지는 황하 및 고황하기원 물질이고, 이외에 양자강과 금강으로부터 공급된 물질과 황해 난류수에 의해 운반된 생물기원 물질의 영향도 다소 있는 것으로 해석된다.