Evidence for gapped spin-wave excitations in the frustrated Gd2Sn2O7 pyrochlore antiferromagnet from low-temperature specific heat measurements

摘要

We have measured the low-temperature specific heat of the geometricallyfrustrated pyrochlore Heisenberg antiferromagnet Gd2Sn2O7 in zero magneticfield. The specific heat is found to drop exponentially below approximately 350mK. This provides evidence for a gapped spin-wave spectrum due to an anisotropyresulting from single ion effects and long-range dipolar interactions. The dataare well fitted by linear spin-wave theory, ruling out unconventional lowenergy magnetic excitations in this system, and allowing a determination of thepertinent exchange interactions in this material.