• Journal of the Korean Magnetics Society
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• v.8 no.3
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• pp.144-149
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• 1998

A new method to calculate the spin reorientation angle of cone anisotropy from magnetization curves of magnetically aligned powder is suggested. The spin reorientation angle of polycrystalline $Nd_2Fe_{14}B$ determined by this method coincided with the results obtained from torque magnetometry or magnetization measurements on single crystal. The underestimation of about 9% is expected if the basal plane anisotropy is neglected in determination of the spin reorientation angle of $Nd_2Fe_{14}B$ at 4.2 K.

• Journal of the Korean Magnetics Society
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• v.8 no.5
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• pp.271-274
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• 1998

Spin reorientation and magnetocrystalline anisotropy of magnetically aligned $(Nd_{1-x}R_x)_2Fe_{14}B$ (R=Y, Pr) power were studied. The spin reorientation temperature $(T_{SR})$ of $(Nd_{1-x}R_x)_2Fe_{14}B$ decreases linearly by increasing Pr-substitution with the ratio of ${\Delta}T_{SR}=-1.35$ K/Pr at.% in composition range of 0$\leq$x$\leq$0.75. The spin reorientation temperature of $(Nd_{1-x}R_x)_2Fe_{14}B$ decreases by increasing Pr-substitution to 118 K (x=0.5) then increases to 122 K (x=0.75). The spin reorientation angle at 4.2 K decreases by increasing rare earth substitution with the ratio of $\Delta$SRA=-0.073$^{\circ}$/Y at.% and $\Delta$SRA=-0.258$^{\circ}$/Pr at.% in composition range of 0$\leq$x$\leq$0.5. The spin reorientation is expected to disappear at x$\geq$0.9 in case of $(Nd_{1-x}R_x)_2Fe_{14}B$ and at x$\geq$0.8 in case of $(Nd_{1-x}R_x)_2Fe_{14}B$.

• Proceedings of the Korean Magnestics Society Conference
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• 2007.05a
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• pp.240.2-240.2
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• 2007

• Journal of Magnetics
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• v.19 no.2
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• pp.126-129
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• 2014

We report the crystallographic and magnetic properties of $Ni_{0.3}Fe_{0.7}Ga_2S_4$ by means of X-ray diffractometer (XRD), a superconducting quantum interference device (SQUID) magnetometer, and a M$\ddot{o}$ssbauer spectroscopy. In particular, $Ni_{0.3}Fe_{0.7}Ga_2S_4$ was studied by M$\ddot{o}$ssbauer analysis for evidence of spin reorientation. The chalcogenide material $Ni_{0.3}Fe_{0.7}Ga_2S_4$ was fabricated by a direct reaction method. XRD analysis confirmed that $Ni_{0.3}Fe_{0.7}Ga_2S_4$ has a 2-dimension (2-D) triangular lattice structure, with space group P-3m1. The M$\ddot{o}$ssbauer spectra of $Ni_{0.3}Fe_{0.7}Ga_2S_4$ at spectra at various temperatures from 4.2 to 300 K showed that the spectrum at 4.2 K has a severely distorted 8-line shape, as spin liquid. Electric quadrupole splitting, $E_Q$ has anomalous two-points of temperature dependence of $E_Q$ curve as freezing temperature, $T_f=11K$, and N$\acute{e}$el temperature, $T_N=26K$. This suggests that there appears to be a slowly-fluctuating "spin gel" state between $T_f$ and $T_N$, caused by non-paramagnetic spin state below $T_N$. This comes from charge re-distribution due to spin-orientation above $T_f$, and $T_N$, due to the changing $E_Q$ at various temperatures. Isomer shift value ($0.7mm/s{\leq}{\delta}{\leq}0.9mm/s$) shows that the charge states are ferrous ($Fe^{2+}$), for all temperature range. The Debye temperature for the octahedral site was found to be ${\Theta}_D=260K$.

• Bulletin of the Korean Chemical Society
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• v.10 no.5
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• pp.430-433
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• 1989

Molecular reorientation of oblate symmetric top molecules in the presence of internal rotation is investigated and an analytic expression for the spin-rotational relaxation rate of a nucleus attached to the internal rotor is obtained as a function of the internal angular momentum correlation time. The overall reorientation of the symmetric top is treated by the anisotropic rotational diffusion and the internal rotation is assumed to undergo modified extended rotational diffusion. The result is compared with the previous work for the prolate symmetric top molecule and it is shown that both results reduce to the same expression in the spherical top limit.

• Journal of the Korean Chemical Society
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• v.19 no.3
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• pp.149-155
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• 1975

Pivalic acid, which has a globular shape and is a plastic crystal, has been examined by means of temperature-dependent with-line proton magnetic resonance spectroscopy. Results of temperature-dependent line width, second moment, and spin-lattice relaxation time studies of pivalic acid were interpreted in terms of dynamic behavior and hydrogen bonding. The dynamic behavior consists of superimposed reorientation of the methyl groups about their three-fold axes$(C_3) and of the molecule about the central C-C bond(C_3'),$ general molecular reorientation about the center of gravity, and molecular self-diffusion. Activation energies for the motional processes have been obtained from line width measurements using the modified Bloembergen, Purcell, and Pound theory and from spin-lattice relaxation time measurements. The results were compared with the Pople-Karasz theory of fusion and the agreement was found to be poor. The discrepancy was interpreted in terms of hydrogen bonding in this molecule.

• Proceedings of the Optical Society of Korea Conference
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• 2002.11a
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• pp.258-259
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• 2002

• Journal of Magnetics
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• v.13 no.2
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• pp.76-80
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• 2008

This study examined the magnetic properties of ultrathin Fe/Ni films on a Cu(001) surface using the full potential linearized augmented plane wave (FLAPW) method. The magnetic moment of Fe/Ni films was found to be insensitive to strain. Nevertheless, strain had a significant influence on the magnetization direction. For example, Fe/Ni films showed a thickness-dependent spin reorientation transition in the presence of strain, while the Fe/Ni films grown pseudomorphically on Cu(001) always showed perpendicular magnetization. In addition, the theoretically calculated X-ray magnetic circular dichroism (XMCD) was examined.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.78-79
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• 2002

It is well known that surface and interface roughnesses greatly affect the magnetic properties such as magnetic domain structure, magnetization reversal, magnetoresistance, and spin reorientation transition (SRT) of ultrathin magnetic films. Therefore, recent studies focus on artificially roughened surface, since it could be possible to systematically understand the effect of roughness on the magnetic properties as well as to obtain the desirable magnetic properties by artificially creating the surface structure and morphology. (omitted)

• Proceedings of the Korean Magnestics Society Conference
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• 1997.05a
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• pp.88-89
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• 1997