-USにおけるS核NMR

S NMR study in -US

酒井 宏典   ; 徳永 陽  ; 神戸 振作  ; Ramakrishna, S. K.*; Reyes, A. P.*; Rosa, P. F. S.*; Ronning, F.*; Thompson, J. D.*; Bauer, E. D.*

Sakai, Hironori; Tokunaga, Yo; Kambe, Shinsaku; Ramakrishna, S. K.*; Reyes, A. P.*; Rosa, P. F. S.*; Ronning, F.*; Thompson, J. D.*; Bauer, E. D.*

ウランカルコゲナイド-USは常磁性体で、室温付近では半金属的伝導を示し、低温では90K程度の狭いバンドギャップをもつ半導体的伝導へクロスオーバーを示すことが知られ、低温において大きな磁気抵抗効果を示す。本系における微視的磁性を明らかにするためにS同位体濃縮を行い、核磁気共鳴(NMR)実験を行なった。当日は、強磁場NMR実験結果も示して、本系の微視的な磁気特性について議論したい。

Uranium disulfide -US is a paramagnetic semiconductor with a narrow band gap of 90 K at low temperatures, whereas above 80 K it is a semimetal with an extremely low density of carriers. Another characteristic feature in -US is the strong response of the electrical resistivity to magnetic field. The magnetoresistance is similar to that of colossal magnetoresistance materials but very anisotropic. In order to clarify the microscopic spin dynamics in -US, nuclear magnetic resonance experiments have been performed. Since the natural concentration of S nuclei () is only 0.76%, isotopic enrichment to 50% has been carried out. In the presentation, we would like to discuss about the microscopic magnetism in -US to show the NMR results under high fields.