Ultrasonic Team (T. Yanagisawa, Hokkaido Univ,)    

研究日誌
2011-6/16「単結晶育ちました」

Jun 16, 2011
Diary 20110616

私個人的には初挑戦となる単結晶をflux法で作っています。例の如くカゴ状結晶構造を持つ化合物ですが、まずは軽希土類を内包する単結晶の育成に成功しました。研究室に配属されたばかりの4年生諸君も熱意を持って試料作成を手伝ってくれています。福島の原発事故以降、新聞やテレビでよく目にするウラン(U)やトリウム(Th)といった放射性元素が内包されたカゴ状化合物にも近々挑戦する予定です。乞うご期待。

"More Is Different" T-shirts

May 12, 2011
More Is Different Elephant More Is Different T-shirts

 研究室でプリントTシャツを作る計画があります。

この記事には続きがあります:続きを読む ...

Earthquakes

Mar 11, 2011
Dear Friends and Colleagues,

We deeply appreciate your concern.
At Hokkaido University, no one was injured, and no damage was done to any of the buildings resulting from the present earthquakes. But we felt no small quake even in Sapporo.
TV news are continuously broadcasting frightful spectacles of the east side of Japan. The present earthquake makes us feel tiny and powerless against natural disasters and nuclear plant accidents.
However, everyone is hanging on to overcome the challenges we are facing.
I would like to pray for the earthquake/tsunami victims and express my condolences to their relatives and friends.

Regards,

Tatsuya Yanagisawa

研究日誌
2011-2/19「KEK-PF」

Feb 19, 2011
Diary 20110219 管理区域入り口 KEK入り口 測定中 フォトンファクトリーのとあるビームライン 隠れた秩序状態にあるURu2Si2

 今年のバレンタインデーは高エネルギー加速器研究機構のフォトンファクトリーで迎えました.

この記事には続きがあります:続きを読む ...


Topics: Double ultrasonic dispersions due to rattling in SmOs4Sb12

Feb 08, 2011
Magnetic-Field-Independent Ultrasonic Dispersions due to Rattling in the Magnetically Robust Heavy Fermion System SmOs4Sb12
Tatsuya YANAGISAWA, Yoichi IKEDA, Hitoshi SAITO, Hiroyuki HIDAKA, Hiroshi AMITSUKA, Koji ARAKI, Mitsuhiro AKATSU, Yuichi NEMOTO, Terutaka GOTO, Pei-Chun HO, Ryan E. BAUMBACH, and M. Brian MAPLE

Elastic properties of the filled skutterudite compound SmOs4Sb12 have been investigated by ultrasonic measurements. The elastic constant C12(\omega) shows two ultrasonic dispersions at ∼15 K and ∼53 K for frequencies \omega between 33 and 316 MHz, which follow a Debye-type formula with Arrhenius-type temperature-dependent relaxation times, and remain unchanged even with applied magnetic fields up to 10 T. The corresponding activation energies were estimated to be E2 = 105 K and E1 = 409 K, respectively. The latter, E1, is the highest value reported so far in the Sb-based filled skutterudites. The presence of magnetically robust ultrasonic dispersions in SmOs4Sb12 implies a possibility that an emergence of a magnetically insensitive heavy fermion state in this system is associated with a novel local charge degree of freedom which causes the ultrasonic dispersion.


J. Phys. Soc. Jpn. 80 (2011) 043601.

(also available on cond-mat/1010.1387)

SmOs_4Sb_12 Ultrasonic Dispersion

Figures (a) Comparison of the ultrasonic dispersions that appear in elastic constant C11 of ROs4Sb12 (R = La-Sm) at several frequencies. Lower arrowheads with numbers 1 and 2 indicate the relaxation point \omega\taui ∼ 1 for i = 1 and 2, respectively. (\omega is ultrasonic frequency and \tau is relaxation time) The displayed data have been shifted to eliminate overlapping with each other and the SmOs4Sb12 data are magnified three times for the \Delta C11/C11-axis. (b) Arrhenius plots of the characteristic parameters of the ultrasonic dispersions (Attempt time: \tau0(i), Activation Energy: Ei) for ROs4Sb12 (R = La-Sm).

(*This research was performed at UC San Diego, Hokkaido University, and Niigata University in 2010.)
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