https://doi.org/10.1007/s100510170177
Incommensurate modulated magnetic structure in orthorhombic EuPdSb
1
CEA, Centre d'Études de Saclay, Service de Physique de l'État
Condensé, 91191 Gif-sur-Yvette, France
2
Department of Physics, Tohoku University, Sendai 980-8578, Japan
3
Laboratoire de Magnétisme Louis Néel, CNRS, 38042 Grenoble,
France
Corresponding author: a bonville@spec.saclay.cea.fr
Received:
17
January
2001
Revised:
20
March
2001
Published online: 15 June 2001
Orthorhombic EuPdSb is known to undergo two magnetic transitions,
at 12 K and at K, and in phase III (T< 12 K), single
crystal magnetisation data have shown that the spin structure is collinear
antiferromagnetic, with magnetic moments along the crystal a
axis. From a 151Eu Mössbauer absorption study, we show that, at any
temperature within phase III, all the moments have equal sizes, and that
in phase II (12 K< T < 18 K) the magnetic structure is modulated and
incommensurate with the lattice spacings. The modulation is close to a pure
sine-wave
just below
K, and it squares up as temperature is lowered. We
measured the thermal variations of the first and third harmonics of the
moment modulation, and we could
determine the first and third harmonics of the exchange coupling.
We furthermore show that the antiferromagnetic-incommensurate transition
at 12 K is strongly first order, with a hysteresis of 0.05 K, and that
the incommensurate-paramagnetic transition at 18 K is weakly first order.
Finally, we present an explanation of the spin-flop transition
observed in the single crystal magnetisation data in phase III when
in terms of an anisotropic molecular field tensor.
PACS: 75.30.Fv – Spin-density waves / 76.80.+y – Mössbauer effect, other gamma-ray spectroscopy / 75.30.Et – Exchange and superexchange interactions
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2001