Eur. Phys. J. B 57, 365-370 (2007)
https://doi.org/10.1140/epjb/e2007-00184-5

Magnetic properties of YbNi₅ from ¹⁷⁰Yb Mössbauer and magnetisation measurements

CEA, Centre d'Études de Saclay, DSM/DRECAM/Service de Physique de l'État Condensé, 91191 Gif-sur-Yvette, France

Corresponding author: ^a hodges@dsm-mail.saclay.cea.fr

Received: 12 March 2007
Published online: 29 June 2007

Abstract

From Yb¹⁷⁰ Mössbauer measurements on YbNi₅, we establish: the Yb³⁺ ground state Kramers doublet is well isolated and has uniaxial anisotropy, the compound magnetically orders at 0.55 K, the Yb³⁺ moments are aligned along the hexagonal axis, they have a saturated value of 3.9μ_B and a thermal variation close to a mean field S = 1/2 law. We obtain the strength of the Yb³⁺–Yb³⁺ coupling which we find is considerably smaller than that between the rare earths (R³⁺) in the other RNi₅. From a study of the spin dynamics, we find that dynamic short range order is present just above the ordering temperature and that above 2 K, the relaxation rate of the paramagnetic Yb³⁺ spins follows a T-linear Korringa law with a relatively pronounced slope which we link to a high density of states at the Fermi level. Magnetic susceptibility and magnetisation measurements establish the ferromagnetic nature of the Yb³⁺–Yb³⁺ coupling. We comment on the Yb³⁺ crystal field properties.