Magnetically Superior and Easy to Handle L10-FePt Nanocrystals

We report a successful synthesis of monodisperse L10-FePt nanocrystals which are not only superior in magnetism but also easy to handle through being dispersible in solvents. Thanks to a thick SiO2-coating, the thermal treatment needed to form the L10 structure can be done even at 900 oC without inducing coalescence and coarsening. The protecting shell was thereafter removed in a specific way that enabled us to recover the L10-FePt nanocrystals in a water-dispersion. The SiO2-coated nanocrystals show a high coercivity of 18.5 kOe at room temperature in spite of their core size of only 6.5 nm in diameter, and the hysteresis loop of the water-dispersed nanocrystals, which were frozen under an external field, was almost rectangular indicating that their magnetic and structural orientation could be attained.Comment: 14 pages, 5 figure

Microscopic Characterization of the L10-FePt Nanoparticles Synthesized by the SiO2-Nanoreactor Method

We investigated magnetic properties of the L10-FePt nanoparticles synthesized by the SiO2-nanoreactor method by means of Moessbauer spectroscopy from the microscopic point of view. Almost all of the nanoparticles were revealed to have nearly the same Moessbauer hyperfine parameters as those of the bulk L10-FePt alloy, indicating that they have well-defined L10 structure equivalent to the bulk state in spite of their small size of 6.5 nm.Comment: 13 pages, 4 figure

Formation of random singlets in the nanocrystalline quasi-one-dimensional spin-1/2 antiferromagnet Sr21Bi8Cu2(CO3)2O41

Induced by quenched disorder, random-singlet states occur in a variety of low-dimensional spin-1/2 antiferromagnets, some of them candidates for quantum spin liquids. Here we report measurements of the specific heat, magnetization, and magnetic susceptibility of nanocrystalline Sr21Bi8Cu2(CO3)2O41, a quasi-one-dimensional spin-1/2 antiferromagnet with alternating bonds. The results uncover the predominant presence of random-singlet spin pairs in this material, with a logarithmic probability distribution, P(J), of the renormalized, emergent exchange interaction, J, in zero magnetic field and P(J) proportional to 1/J in magnetic fields. We postulate that these unexpected J dependences, in contrast to the usual P(J) \propto 1/$J^\gamma$ with 0 < $\gamma$ < 1, and possibly also the dichotomy, arise from the finite size of the nanocrystals. Scaling functions for the specific heat and magnetization reproduce our magnetocaloric-effect data, with no adjustable parameters

チイキ シゼン エネルギー ノ ジッセン リヨウ システム

A nature energy project, composed of a solar system, a windmill-type heat exchange system and a micro water wheel power system, was designed and is now under construction at Saeki-cho, Okayama Prefecture. Recent five year\u27data has been recorded into Automated Meteorological Data Acquisition System was referred for the best design. Total cost of this project is supported by both the public subsidies of the Ministry of International Trade and Industry and the one of Okayama Prefecture

ソクド チョウリョク ノ ビショウ ヘンカ ケンシュツ ト ソノ オウヨウ

A sinker with a non-stretched fine flexible string fall down with the sinker naturally, and both the speed and tension of its drawing-out string are individually measured. It is thought that a sinker will meet with an obstacle, if both sudden irregularities are observed at the same time upon motion of the string. In this case, a general stepping motor are employed in measurments of the speed and a tork-less special encorder are used in detection of the tension as sensors

ネツ ルミネッセンス 2ジゲン ヨミトリ システム

熱ルミネッセンス[TL]2次元読み取りシステムを開発した。このシステムを使った応用として, 人工のTL-sheet(BaSO_4 : Eu)を用いて高エネルギー宇宙線シャワーの検出を行なった例と, 天然の試料(鍾乳石, 花崗岩)のTL空間分布を測定した例を示す.A spatial distribution read-out system of thermoluminescence [TL] is developed. This system is applied to artificial TL-sheets (BaSO_4 : Eu) for detecting high energy cosmic ray showers and to inhomogeneous materials for measuring natural TL spatial distributions of stalactite and Mannari-granite

ジカン ブンカイ ブンコウ ケイソク システム

秒のオーダで分光の強度変化が起こる現象を測定する分光計測システムを開発した.このシステムを使えば, 分光量が微弱で, かつ時間変化する(例えば熱ルミネッセンス)発光スペクトルを紫外から可視光にわたって計測することができる.A new system of spectroscopy for a time varying phenomenon in a order of second is introduced. It consists of a monochromator, an image intensifier and TV-camera system. Spectral images recorded onto video tape are processed by an image processor interfaced to an personal computer. The low intensity and time-dependent spectroscopy yield (for example, thermoluminescent spectrum) is able to be measured in the range from ultra violet to visual light by using the system