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Titolo:
First-order phase transition in UO2: U-235 and O-17 NMR study - art. no. 104404
Autore:
Ikushina, K; Tsutsui, S; Haga, Y; Yasuoka, H; Walstedt, RE; Masaki, NM; Nakamura, A; Nasu, S; Onuki, K;
Indirizzi:
Japan Atom Energy Res Inst, Adv Sci Res Ctr, Tokai, Ibaraki 3191195, JapanJapan Atom Energy Res Inst Tokai Ibaraki Japan 3191195 aki 3191195, Japan Japan Atom Energy Res Inst, Dept Mat Sci, Tokai, Ibaraki 3191195, Japan Japan Atom Energy Res Inst Tokai Ibaraki Japan 3191195 aki 3191195, Japan Osaka Univ, Fac Engn Sci, Dept Phys Mat, Osaka 5608531, Japan Osaka Univ Osaka Japan 5608531 Sci, Dept Phys Mat, Osaka 5608531, Japan Osaka Univ, Grad Sch Sci, Toyonaka, Osaka 5600043, Japan Osaka Univ Toyonaka Osaka Japan 5600043 i, Toyonaka, Osaka 5600043, Japan
Titolo Testata:
PHYSICAL REVIEW B
fascicolo: 10, volume: 6310, anno: 2001,
pagine: 4404 -
SICI:
0163-1829(20010301)6310:10<4404:FPTIUU>2.0.ZU;2-Y
Fonte:
ISI
Lingua:
ENG
Soggetto:
ANTIFERROMAGNETIC STATE; NEUTRON-DIFFRACTION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
--discip_EC--
Citazioni:
36
Recensione:
Indirizzi per estratti:
Indirizzo: Ikushina, K Japan Atom Energy Res Inst, Adv Sci Res Ctr, Tokai, Ibaraki 3191195, Japan Japan Atom Energy Res Inst Tokai Ibaraki Japan 3191195 Japan
Citazione:
K. Ikushina et al., "First-order phase transition in UO2: U-235 and O-17 NMR study - art. no. 104404", PHYS REV B, 6310(10), 2001, pp. 4404

Abstract

A nuclear magnetic resonance (NMR) study is reported for a 5f-cooperative Jahn-Teller (JT) system with antiferromagnetic ordering, UO2, where we haveperformed magnetic actinide (U-235) as well as nonmagnetic ligand (O-17) NMR studies in a SS-electron system. The observed U-235 hyperfine interaction is consistent with an axially symmetric Sf-wave-function character for U4 below a first-order transition temperature T-N = 30.8 K Thus, the orbitaldegeneracy in the cubic crystalline field is lifted by a magnetic orderingcombined with a JT distortion. On the other hand, modulation phenomena in the O-17 spin-echo decay provide evidence of a lattice distortion just below T-N, which gives rise to an axially symmetric electric-field gradient at the oxygen sites. These results indicate that, in a cooperative JT transition which occurs as a result of coupling between 5f quadrupoles and lattice distortion, the behavior of the 5f quadrupoles can be investigated using uranium NMR, white the lattice distortion can be studied with the nonmagneticLigand NMR. Among magnetic structures and JT distortions, proposed on the basis of neutron scattering experiments and theoretical work, the noncollinear 3k-type structure is the most likely, because either the 1k or 2k wouldcause an orthorhombic distortion. With respect to low-energy spin-wave excitations, nuclear spin-lattice relaxation rates T-1(-1) at both sites shaw a T-7 behavior below T-N, which suggests the presence of gapless excitations due to strong magnon-phonon coupling.

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Documento generato il 19/09/20 alle ore 21:24:05