Ising versus XY Anisotropy in Frustrated R2Ti2O7 Compounds as “Seen” by Polarized Neutrons
Ising versus XY Anisotropy in Frustrated R2Ti2O7 Compounds as “Seen” by Polarized Neutrons
H. Cao,
1 A. Gukasov,
1 I. Mirebeau,
1 P. Bonville,
2 C. Decorse,
3 and G. Dhalenne
3
Phys. Rev. Lett. 103, 056402 (2009)
1Laboratoire Léon Brillouin,
2Service de Physique de l'Etat Condensé,
3Laboratoire de Physico-Chimie de l'Etat Solide
Received 8 April 2009; published 29 July 2009
We studied the field induced magnetic order in R2Ti2O7 pyrochlore compounds with either uniaxial (R=Ho, Tb) or planar (R=Er, Yb) anisotropy, by polarized neutron diffraction. The determination of the local susceptibility tensor {,} provides a universal description of the field induced structures in the paramagnetic phase (2–270 K), whatever the field value (1–7 T) and direction. Comparison of the thermal variations of || and with calculations using the rare earth crystal field shows that exchange and dipolar interactions must be taken into account. We determine the molecular field tensor in each case and show that it can be strongly anisotropic.