• 전기전자학회논문지
• /
• 제22권1호
• /
• pp.61-67
• /
• 2018

We investigated theoretically the magnetic field dependence of the quantum optical transition of qusi 2-Dimensional Landau splitting system, in CdS and ZnO. In this study, we investigate electron confinement by square well confinement potential in magnetic field system using quantum transport theory(QTR). In this study, theoretical formulas for numerical analysis are derived using Liouville equation method and Equilibrium Average Projection Scheme (EAPS). In this study, the absorption power, P (B), and the Quantum Transition Line Widths (QTLWS) of the magnetic field in CdS and ZnO can be deduced from the numerical analysis of the theoretical equations, and the optical quantum transition line shape (QTLS) is found to increase. We also found that QTLW, ${\gamma}(B)_{total}$ of CdS < ${\gamma}(B)_{total}$ of ZnO in the magnetic field region B<25 Tesla.

• 한국자기공명학회논문지
• /
• 제23권2호
• /
• pp.40-45
• /
• 2019

The phase transition temperatures and thermodynamic properties of $(NH_4)_2MnCl_4{\cdot}2H_2O$ grown by the slow evaporation method were studied using differential scanning calorimetry and thermogravimetric analysis. A structural phase transition occurred at temperature $T_{C1}$ (=264 K), whereas the changes at $T_{C2}$ (=460 K) and $T_{C3}$ (=475 K) seemed to be chemical changes caused by thermal decomposition. In addition, the chemical shift and the spin-lattice relaxation time $T_{1{\rho}}$ were investigated using $^1H$ magic-angle spinning nuclear magnetic resonance (MAS NMR), in order to understand the role of $NH_4{^+}$ and $H_2O$. The rise in $T_{1{\rho}}$ with temperature was related to variations in the symmetry of the surrounding $H_2O$ and $NH_4{^+}$.

• Bulletin of the Korean Chemical Society
• /
• 제24권5호
• /
• pp.573-578
• /
• 2003

The structural, magnetic, and transport properties of a mono-layered manganite $La_{0.7}Sr_{1.3}MnO_{4+{\delta}}$ were investigated using variable temperature neutron powder diffraction as well as magnetization and transport measurements. The compound adopts the tetragonal I4/mmm symmetry and exhibits no magnetic reflection in the temperature region of 10 K ≤ T ≤ 300 K. A weak ferromagnetic (FM) transition occurs about 130 K, which almost coincides with the onset of a metal-insulator (M-I) transition. Extra oxygen that occupies the interstitial site between the [(La,Sr)O] layers makes the spacing between the [MnO₂] layers shorten, which enhances the inter-layer coupling and eventually leads to the M-I transition. We also found negative magneto resistance (MR) below the M-I transition temperature, which can be understood on the basis of the percolative transport via FM metallic domains in the antiferromagnetic (AFM) insulating matrix.

• Journal of Magnetics
• /
• 제12권4호
• /
• pp.137-140
• /
• 2007

We have studied the temperature dependent magnetic properties and crystalline phase transitionn in small amount Fe doped nickel chromite. The Crystalline structure of $NiCr_{1.7}Fe_{0.3}O_4$ is spinel cubic (Fd-3m) structure with a lattice constant $a_0=8.317\AA$ at room temperature. The magnetic $N\acute{e}el$ temperature $(T_N)$ of the Fe doped nickel chromite sample is determined to be 250 K. The $M\ddot{o}ssbauer$ spectra exhibit that there are two magnetic phases with the two different sites for the $Cr^{3+}$ ions. The spectrum at 4.2 K is fitted to two magnetic components of the magnetic hyperfine fields $H_{hf}=496$ and 485 kOe. From the spectrum at 295 K, the electric quadrupole splittings are observed with large values of 0.49 and 0.50 mm/s, respectively. The values of the isomer shifts at all temperature ranges show that the Fe ions are ferric states. We are suggested that the dynamic Jahn-Teller distortion and anisotropic magnetic relaxation effects due to the crystalline phase transition.

• 한국진공학회지
• /
• 제7권s1호
• /
• pp.1-6
• /
• 1998

The influence of the order-disorder structural transition on the magnetic and mageto-optical, and transport properties of Fe-Al and Co-Al alloy films has been investigated. The disordered states in the alloy films were prepared by vapor quenching deposition on glass substrates cooled by liquid nitrogen. The experimental study of the magento-optical properties of the ordered and disordered Fe-Al and Co-Al alloy films has been carried out in 1.05-5.0 eV energy range at room temperature. The transport properties have been measured in 2-300K temperature range with and without magnetic field of 0.5T. The influence of the order-disorder structural transition on the magnetic and magneto-optical properties was discussed by using the effective medium approximation and the structural defect approach. That on the temperature dependence of the resistivity was analyzed in a framework of the partial localization of the electronic states and the variable range hopping conductivity.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 1999년도 추계연구발표회 논문개요집
• /
• pp.74-75
• /
• 1999

• 한국자기학회지
• /
• 제3권4호
• /
• pp.277-283
• /
• 1993

세개의 오스테 나이트계의 Fe-Cr-Ni 스테인레스 합금강들의 DC 자화율의 온도의존성을 4.2-300 K 온도영역에서 측정하였다. 측정결과 두개의 합금강들은 two-magnetic-phase 모델(spin glass와 초상자성)을 만족하였으며 나머지 하나는 자기적 2중 천이현상을 나타내었다. 또한 Ni/Cr의 비가 증가할수록 자화율의 최 대값이 증가하고 이 값을 나타내는 온도는 감소하였다.

• Journal of Magnetics
• /
• 제16권2호
• /
• pp.134-139
• /
• 2011

Magnetic properties of highly zinc-substituted manganese ferrites are discussed on the basis of cation distribution. High throughput neutron powder diffractometry indicates that the prepared samples possess a nearly normal spinel structure, where the substitution of nonmagnetic zinc ions mainly causes the dilution of magnetic ions in the A-sublattice and consequently affects bond-randomness in the B-sublattice. On the other hand, the estimated occupancy of manganese ions in the B site indicates that random anisotropy effects due to local Jahn-Teller distortions gradually weaken with the substitution. Bulk magnetometry indicates that the substitution smears the transition from a paramagnetic phase to a soft-magnetic phase. Furthermore, at lower temperatures, such a soft-magnetic phase is destabilized and a magnetic glassy state appears. These features of the magnetic properties of dilute spinel ferrites are discussed from the viewpoint of the above-mentioned various types of disorders.

• 한국자기학회:학술대회 개요집
• /
• 한국자기학회 2008년도 Asian Magnetics Conference
• /
• pp.82.1-82.1
• /
• 2008

• Current Applied Physics
• /
• 제18권12호
• /
• pp.1605-1608
• /
• 2018

$Gd_{1-x}Ho_xNi$ melt-spun ribbons were fabricated by a single-roller melt spinning method. All the compounds crystallize in an orthorhombic CrB-type structure. The Curie temperature ($T_C$) was tuned between 46 and 99 K by varying the concentration of Gd and Ho. A spin reorientation (SRO) transition is observed around 13 K. Different from $T_C$, the SRO transition temperature is almost invariable for all compounds. Two peaks of magnetic entropy change (${\Delta}S_M$) were found. One at the higher temperature range was originated from the paramagnet-ferromagnet phase transition and the other at the lower temperature range was caused by the SRO transition. The maximum of ${\Delta}S_M$ around $T_C$ is almost same. The other maximum of ${\Delta}S_M$ around SRO transition, however, had significantly positive relationship with x. It reached a maximum about $8.2J\;kg^{-1}\;K^{-1}$ for x = 0.8. Thus double large ${\Delta}S_M$ peaks were obtained in $Gd_{1-x}Ho_xNi$ melt-spun ribbons with the high Ho concentration. And the refrigerant capacity power reached a maximum of $622J\;kg^{-1}$ for x = 0.6. $Gd_{1-x}Ho_xNi$ ribbons could be good candidate for magnetic refrigerant working in the low temperature especially near the liquid nitrogen temperature range.