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Durham University

Department of Physics

Staff profile

Publication details for Professor Tom Lancaster

Kirschner, Franziska K. K., Johnson, Roger D., Lang, Franz, Khalyavin, Dmitry D., Manuel, Pascal, Lancaster, Tom, Prabhakaran, Dharmalingam & Blundell, Stephen J. (2019). Spin Jahn-Teller antiferromagnetism in CoTi2O5. Physical Review B 99(6): 064403.

Author(s) from Durham

Abstract

We have used neutron powder diffraction to solve the magnetic structure of orthorhombic CoTi2O5, showing
that the long-range ordered state below 26 K identified in our muon-spin rotation experiments is antiferromagnetic with propagation vector k = (±1
2 , 1
2 , 0) and moment of 2.72(1)μB per Co2+ ion. This long-range
magnetic order is incompatible with the experimentally determined crystal structure because the imposed
symmetry completely frustrates the exchange coupling. We conclude that the magnetic transition must therefore
be accompanied by a spin Jahn-Teller effect which lowers the structural symmetry and thereby relieves the
frustration. These results show that CoTi2O5 is a highly unusual low-symmetry material exhibiting a purely
spin-driven lattice distortion critical to the establishment of an ordered magnetic ground state.