TY - JOUR

T1 - Low-temperature magnetic properties of NpNi5

AU - Hen, A.

AU - Colineau, E.

AU - Eloirdi, R.

AU - Griveau, J. C.

AU - Magnani, N.

AU - Wilhelm, F.

AU - Rogalev, A.

AU - Sanchez, J. P.

AU - Shick, A. B.

AU - Halevy, I.

AU - Orion, I.

AU - Caciuffo, R.

PY - 2014/8/11

Y1 - 2014/8/11

N2 - We present the result of an extended experimental characterization of the hexagonal intermetallic Haucke compound NpNi5. By combining macroscopic and shell-specific techniques, we determine the 5f-shell occupation number nf close to 4 for the Np ions, together with orbital and spin components of the ordered moment in the ferromagnetic phase below TC=16 K (μS=-1.88 μB and μL=3.91 μB). The apparent coexistence of ordered and disordered phases observed in the Mössbauer spectra is explained in terms of slow relaxation between the components of a quasitriplet ground state. The ratio between the expectation value of the magnetic dipole operator and the spin magnetic moment (3Tz/Sz=+1.43) is positive and large, suggesting a localized character of the 5f electrons. The angular part of the spin-orbit coupling (- ·s- =-5.55) is close to the value of -6.25 calculated for trivalent Np ions in intermediate coupling approximation. The results are discussed against the prediction of first-principle electronic structure calculations based on the spin-polarized local spin density approximation plus Hubbard interaction, and of a mean field model taking into account crystal field and exchange interactions.

AB - We present the result of an extended experimental characterization of the hexagonal intermetallic Haucke compound NpNi5. By combining macroscopic and shell-specific techniques, we determine the 5f-shell occupation number nf close to 4 for the Np ions, together with orbital and spin components of the ordered moment in the ferromagnetic phase below TC=16 K (μS=-1.88 μB and μL=3.91 μB). The apparent coexistence of ordered and disordered phases observed in the Mössbauer spectra is explained in terms of slow relaxation between the components of a quasitriplet ground state. The ratio between the expectation value of the magnetic dipole operator and the spin magnetic moment (3Tz/Sz=+1.43) is positive and large, suggesting a localized character of the 5f electrons. The angular part of the spin-orbit coupling (- ·s- =-5.55) is close to the value of -6.25 calculated for trivalent Np ions in intermediate coupling approximation. The results are discussed against the prediction of first-principle electronic structure calculations based on the spin-polarized local spin density approximation plus Hubbard interaction, and of a mean field model taking into account crystal field and exchange interactions.

UR - http://www.scopus.com/inward/record.url?scp=84924429356&partnerID=8YFLogxK

U2 - 10.1103/PhysRevB.90.054408

DO - 10.1103/PhysRevB.90.054408

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AN - SCOPUS:84924429356

SN - 1098-0121

VL - 90

JO - Physical Review B - Condensed Matter and Materials Physics

JF - Physical Review B - Condensed Matter and Materials Physics

IS - 5

M1 - 054408

ER -