We have investigated the ${}^{89}\mathrm{Y}$ NMR spectrum and spin lattice relaxation, $T_1$, in the magnetically frustrated pyrochlore ${\mathrm{Y}}_2{\mathrm{Mo}}_2{\mathrm{O}}_7$. We find that upon cooling the spectrum shifts, and broadens asymmetrically. A detailed examination of the low $T$ spectrum reveals that it is constructed from multiple peaks, each shifted by a different amount. We argue that this spectrum is due to discrete lattice distortions and speculate that these distortions relieve the frustration and reduce the system’s energy.

• Received 25 May 2001

DOI:https://doi.org/10.1103/PhysRevLett.87.177201