Neutron scattering study of magnetic structure and metamagnetic transition between low- and high-moment states of NpNiGa{sub 5}

Journal Article · Sun Oct 01 00:00:00 EDT 2006 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PHYSREVB.74.144413· OSTI ID:20853753

Honda, Fuminori; Kaneko, Koji; Jonen, Shintaro; Yamamoto, Etsuji ^[1]; Metoki, Naoto; Haga, Yoshinori ^[1]; Aoki, Dai; Homma, Yoshiya ^[2]; Shiokawa, Yoshinobu ^[1]; Onuki, Yoshichika ^[1]

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1. Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan)
2. Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan)

Systematic neutron scattering experiments have been carried out in order to reveal the magnetic properties of NpNiGa{sub 5}. We have observed a ferromagnetic transition with the magnetic moment parallel to the tetragonal c axis at T{sub C}=30 K. We have also observed antiferromagnetic reflections with the propagation vector q=(1/2 1/2 1/2), coexisting with the ferromagnetic component below T{sub N}=18 K. The direction of the antiferromagnetic component is perpendicular to the c axis, most likely {mu}{sup AF}(parallel sign)<1 1 0>. Spin-polarized neutron scattering experiments have revealed that only Np carries a magnetic moment. The polarization of Ni atom is less than 0.03 {mu}{sub B}/Ni, judging from our experimental accuracy. Thus, we conclude that the magnetic moments of Np atoms exhibit the simple ferromagnetic ordering, T{sub N}<T<T{sub C}, while a canted antiferromagnetic structure appears where T<T{sub N}. A cant angle {theta} of {approx}90 deg. between two adjacent Np moments and a magnetic moment {mu} of {approx}0.8 {mu}{sub B}/Np at 3 K have been estimated. The temperature and the magnetic field dependences of these two components have also been quantitatively analyzed. (i) It is quite unusual that the Np total moment increases with the transition from the ferromagnetic to canted antiferromagnetic structure. (ii) The metamagnetic transition cannot be explained in terms of a simple spin-flip mechanism with competing interactions and anisotropy. (iii) Furthermore, an unusual reduction of the Np magnetic moment is accompanied with the metamagnetic transition. From these results, we concluded that a remarkable change in the 5f electronic state between the ferromagnetic low-moment state and the canted antiferromagnetic high-moment state takes place at T{sub N} and metamagnetic transition.

• OSTI ID: 20853753
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Vol. 74, Issue 14; Other Information: DOI: 10.1103/PhysRevB.74.144413; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANISOTROPY
ANTIFERROMAGNETIC MATERIALS
ANTIFERROMAGNETISM
ATOMS
ELECTRONS
FERROMAGNETIC MATERIALS
GALLIUM ALLOYS
MAGNETIC FIELDS
MAGNETIC MOMENTS
MAGNETIC PROPERTIES
NEEL TEMPERATURE
NEPTUNIUM ALLOYS
NEUTRON DIFFRACTION
NICKEL ALLOYS
POLARIZATION
REFLECTION
SPIN
SPIN FLIP
SPIN ORIENTATION
VECTORS