Glassy relaxation without freezing in a random dipolar-coupled magnet.

We have measured the magnetic susceptibility, chi' + i chi", of the dilute dipolar-coupled Ising magnet LiHo sub (0.045) Y sub (0.955) F sub 4 over six decades of frequency from 0. 02 Hz to 20 kHz. The system behaves as an ideal relaxational glass with Arrhenius behavior in temperature of the peak in chi". Scaling high data from T = 100 mK to T = 300 mK by the peak in high chi" shows an enhanced low frequency response at high temperatures, in contrast to expectations for spin glasses and random field magnets.