Letter to the Editor

doi:10.1088/0953-8984/16/28/L01

LETTER TO THE EDITOR

Phase transitions, partial disorder and multi-k structures in Gd₂Ti₂O₇

J R Stewart et al 2004 J. Phys.: Condens. Matter 16 L321-L326 doi: 10.1088/0953-8984/16/28/L01

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J R Stewart¹, G Ehlers², A S Wills³, S T Bramwell³ and J S Gardner^4,5
¹ Institut Max von Laue-Paul Langevin, 6 rue Jules Horowitz, 38042 Grenoble, France
² SNS Project, Oak Ridge National Laboratory, 701 Scarboro Road, Oak Ridge, TN 37830, USA
³ Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK
⁴ NIST Center for Neutron Research, NIST, Gaithersburg, MD 20899-8562, USA
⁵ Physics Department, Brookhaven National Laboratory, Upton, NY 11973, USA

Abstract. The geometrically frustrated antiferromagnet Gd₂Ti₂O₇ exhibits magnetic behaviour of such complexity that it poses a challenge to both experiment and theory. Magnetic ordering commences at T_N = 1.1 K and there is a further magnetic phase transition at $T^{\prime }=0.7$ K. Here we use neutron diffraction to definitively establish the nature of the phase transition at $T^{\prime }$ and the magnetic structure adopted below this temperature. Between $T^{\prime }$ and T_N the structure is partly ordered, as previously reported. Below $T^{\prime }$ the remaining spins order, but only weakly. The magnetic structure in this temperature range is shown to be a 4-k structure, closely related to the 1-k structure previously suggested. The 4-k and 1-k variants of the structure are distinguished by analysis of the diffuse scattering, which we believe represents a new method of solving the 'multi-k' problem of magnetic structure determination.