title: NMR evidence for triple-q multipole structure in NpO2.
abstract: In order to elucidate the nature of the exotic ordered phase of NpO2 below T(0)=26 K, we have initiated the first 17O-NMR measurements on this system. From the 17O-NMR spectrum, the occurrence of two inequivalent oxygen sites has been confirmed below T0. It has also been shown that the characteristic features of the hyperfine interaction at the oxygen sites are well explained by invoking a hyperfine interaction with field-induced antiferromagnetic moments which appear as a result of the triple-q antiferroquadrupolar order. The NMR findings strongly support the occurrence of the longitudinal triple-q multipole structure in NpO2.
authors.affiliation: ASRC, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Tokunaga
authors.forename: Y
authors.initials: Y
authors.lastname: Homma
authors.forename: S
authors.initials: S
authors.lastname: Kambe
authors.forename: D
authors.initials: D
authors.lastname: Aoki
authors.forename: H
authors.initials: H
authors.lastname: Sakai
authors.forename: E
authors.initials: E
authors.lastname: Yamamoto
authors.forename: A
authors.initials: A
authors.lastname: Nakamura
authors.forename: Y
authors.initials: Y
authors.lastname: Shiokawa
authors.forename: R E
authors.initials: RE
authors.lastname: Walstedt
authors.forename: H
authors.initials: H
authors.lastname: Yasuoka