We have investigated the spin dynamics of Tb${}_2$Ti${}_2$O${}_7$ as a function of magnetic field applied along the $\left[111\right]$ axis using ac susceptibilty and muon-spin relaxation measurements. We find a significant increase in the imaginary part of the magnetic susceptibility at low fields at our lowest investigated temperature and an increased muon-spin relaxation rate in the same field range persisting to higher temperature. Comparing the data from the two techniques we identify three field regions where the dynamic properties of Tb${}_2$Ti${}_2$O${}_7$ appear to be evolving in different ways with crossovers between the regions at $B_1=15$ and $B_2\sim 60$ mT.

• Received 11 May 2011

DOI:https://doi.org/10.1103/PhysRevB.86.094424