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ICOSAHEDRAL CLUSTERS AND MAGNETIC PROPERTIES OF LaCo₁₃ AMORPHOUS AND CRYSTALLINE ALLOYS
K. Fukamichi,A. Fujita,N. Ohashi,M. Hashimoto,E. Matsubara,Y. Waseda 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.5
The atomic structure and magnetic properties of LaCo₁₃ amorphous alloy have been investigated and compared with those of its crystalline counterpart. It has been confirmed that the amorphous alloy is composed of the icosahedral clusters with a NaZn₁₃-type structure. The magnetic moment and the spin-wave stiffness constant obtained from the magnetic measurements in the amorphous state are larger than those in the crystalline state. The Curie temperature estimated from the reduced magnetization curve for the former is much higher than the value for the latter. The localized magnetic moment character in the amorphous state is stronger than that in the crystalline state.
S. Fujieda,A. Fujita,K. Fukamichi,S. Suzuki 한국자기학회 2013 Journal of Magnetics Vol.18 No.2
La1-zNdz(Fe0.88Si0.12)13 and their hydrides were investigated to obtain large magnetocaloric effects (MCEs) in a wide temperature range, including room temperature, for applications in magnetic refrigents. Since the magnetization change due to the itinerant-electron metamagentic (IEM) transition for La1-zNdz(Fe0.88Si0.12)13 becomes larger with increasing z, the isothermal magnetic entropy change ΔSm and the relative cooling power (RCP) are enhanced. In addition, the Curie temperatrue TC of La0.8Nd0.2(Fe0.88Si0.12)13 is increased from 193 to 319 K by hydrogen absorption, with the IEM transition. The maximum value of -ΔSm, -ΔSm<SUP>max</SUP>, in a magnetic field change of 2 T for La0.8Nd0.2(Fe0.88Si0.12)13H1.1 is about 23 J/kg K at TC = 288 K, which is larger than that of 19 J/kg K at TC = 276 K for La(Fe0.88Si0.12)13H1.0. The value of RCP = 179 J/kg of the former is also larger than 160 J/kg of the latter. It is concluded that the partial substitution of Nd improves MCEs in a wide temperautre range, including room temperature.
COERCIVE FIELD AND SPIN - GLASS BEHAVIOR OF AMORPHOUS Y-Fe ALLOYS
A. Fujita,K. Fukamichi 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.5
The coercive field He of amorphous Y-Fe alloys in the spin-glass state has been investigated. For amorphous Y_(10)Fe_(90) alloy, the thermal variations of Hc in the maximum external field Hmax = 300, 600 and 1 k Oe exhibit a maximum. Since spin-glass behavior is strongly affected by external magnetic fields, the maximum point moves to lower temperature with increasing Hmax. The appearance of the maximum in Hc has been discussed in terms of the change of the spin-glass state in the external magnetic field. When the value of Hmax is 55 kOe, the temperature dependence of Hc has no maximum and shows an exponential decrease with increasing temperature. Similar trends have been observed over a wide concentration range. The concentration dependence of Hc is associated with the magnetic phase diagram.
MAGNETIC PROPERTIES OF REPb₂(RE : LIGHT RARE - EARTH ELEMENT) COMPOUNDS
Y. Hattori,R. Sugioka,K. Fukamichi,K. Suzuki,T. Goto 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.5
Systematic studies on the crystal structure and magnetic properties of light rare earth element(RE) compounds with Pb, REPb₂, have been carried out. Their crystal structure has been identified to be a MoSi₂type. The values of the effective magnetic moment for CePb₂ PrPb₂ and NdPb₂ are respectively very close to the theoretical values of RE³+. These three compounds are antiferromagnetic and exhibit a metamagnetic transition. The magnitude of the Neel temperature is proportional to two-thirds of the de Gennes factor. The magnetic entropy change for NdPb₂ is contrast to the value for CePb₂ heavy-fermion compound, comparable to the theoretical value. The magnetic contribution to the temperature dependence of resistivity for PrPb₂ is given by a form of -lnT in a wide temperature range, implying the Kondo system in analogy with CePb₂.
EFFECT OF THE ADDITION OF NI ON GIANT MAGNETORESISTANCE OF Cu - Co AGED RIBBONS
I. J. Kim,J. Echigoya,K. Fukamichi,Y. Shimada 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.5
Giant magnetoresistance (GMR) of Cu_(85-x)Co_(15)Ni_x melt-spun ribbons is closely correlated with the microstructure produced by the spinodal decomposition. The solid solution range is extanded by the replacement of Cu by Ni in the as-quenched state. The wavelengths obtained by subsequent isothermal aging in Cu-Co-Ni ribbons are shorter than those in Cu-Co binary ribbons, resulting in the increase of the surface-to-volume ratio. The largest MR ratio of 8 % in high field has been achieved in the Cu_(80)Co_(15)Ni_5 aged ribbon. The field dependence of MR ratio in low fields becomes larger with the Ni content.