Europhys. Lett.
Volume 63, Number 4, August 2003
Page(s) 597 - 602
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 01 November 2003
DOI: 10.1209/epl/i2003-00568-7
Europhys. Lett., 63 (4) , pp. 597-602 (2003)

Magnetic-field dependence of the magnetic excitations in ordered $\chem{HoNi_{2}B_{2}C}$

N. Cavadini1, M. Schneider1, P. Allenspach1, P. C. Canfield2 and Ph. Bourges3

1  Laboratory for Neutron Scattering, ETH Zürich & Paul Scherrer Institut 5232 Villigen PSI, Switzerland
2  Ames Laboratory, Department of Physics and Astronomy, Iowa State University Ames, IA 50011, USA
3  Laboratoire Léon Brillouin, CEA/CNRS-Saclay 91191 Gif-sur-Yvette, France

(Received 10 December 2002; accepted in final form 16 June 2003)

The effect of an external magnetic field H on the magnetic excitations in ordered $\chem{HoNi_{2}B_{2}C}$ is investigated by inelastic neutron scattering on single crystals for the first time. A Zeeman-like renormalization of the magnetic excitations is observed at fixed T=2 $\un{K}$ and $H\parallel[1,1,0]$ up to H=5 $\un{T}$. Above $H\sim 1.1$ $\un{T}$ the renormalization occurs linearly, following the expectation for the $\chem{Ho^{3+}}$ crystal electric-field levels at finite fields. However, in the range 0<H<1.1 $\un{T}$ clear discontinuities mark the successive metamagnetic transitions reported for the ground state of the title compound. The comparison of the magnetic excitations between the antiferromagnetic ( H<0.4 $\un{T}$), helicoidal ( $0.4
\le H <1.1$ $\un{T}$) and ferromagnetic ( $H \ge 1.1$ $\un{T}$) ground state allows, by first principles, the determination of the leading exchange interactions between the rare-earth ions. The quantitative results are put into the context of recent theoretical models.

75.10.Dg - Crystal-field theory and spin Hamiltonians.
75.30.Et - Exchange and superexchange interactions.
78.70.Nx - Neutron inelastic scattering.

© EDP Sciences 2003