Field Induced Order and Spin Waves in the Pyrochlore Antiferromagnet Tb2Ti2O7

1
Field Induced Order and Spin Waves in the
Pyrochlore Antiferromagnet Tb2Ti2O7
K.C. Rule1, J.P.C. Ruff1, B.D. Gaulin1, S.R.
Dunsiger1, J.P. Clancy1, M.J. Lewis1, H.A.
Dabkowska1, I. Mirebeau2, P. Manuel3, J.S.
Gardner4, Y. Qiu4,5, and J.R.D. Copley4
1McMaster U. (Canada), 2CEA Saclay (France),
3ISIS (UK), 4CHRNS, 5U. Maryland
DMR-0454672
Tb2Ti2O7 is a geometrically frustrated
antiferromagnet in which magnetic Tb3 ions are
located at the vertices of a network of
corner-sharing tetrahedra. High resolution
time-of-flight experiments using the CHRNS DCS
with long wavelength (5 Å and 9 Å) neutrons, in
fields as high as 9 T, reveal a complex
magnetic-field vs temperature phase diagram a
cooperative paramagnet, a polarized paramagnet,
and a high field long range ordered phase.
Panels a, b and c show the measured diffuse
intensity at 1K, integrated over low energies
(-0.5 to 0.5 meV) panel d shows the elastic and
near-elastic scattering integrated over Q,
including the (002) position. As the field is
increased additional Bragg peaks appear and the
diffuse scattering around (002) disappears.
Other measurements, at 0.4 K, show that in the
ordered phase (above 2 T) there are well-defined
spin-wave excitations. These new observations of
complex behavior in Tb2Ti2O7 will hopefully
motivate theoretical study aimed at a more
complete understanding of this enigmatic
material.
K.C. Rule, J.P.C. Ruff, B.D. Gaulin, S.R.
Dunsiger, J.S. Gardner, J.P. Clancy, M.J. Lewis,
H.A. Dabkowska, I. Mirebeau, P. Manuel, Y. Qiu,
and J.R.D.Copley, Phys. Rev. Lett. 96, 177201
(2006).