Eur. Phys. J. B 21, 349-355 (2001)
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

Abstract

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.