μSR study of the “anti-glass” LiHo0.045Y0.955F4

LiHoF4 is a dipolar-coupled Ising ferromagnet with Tc=1.53K. If sufficient dilution is introduced into the system by substituting magnetic Ho atoms with nonmagnetic Y, it becomes glassy. Even though theoretical predictions state that the glassy state should persist down to the lowest Ho concentrations, it has been observed that the system runs into what has been called the “antiglass” phase.The nature of the “antiglass” state is still not understood, and not much experimental data is available. We studied this system at the microscopic scale using μSR. Zero field and longitudinal field measurements were performed from room temperature down to 20mK. We found that the Ho spins remain dynamic down to 20mK with a fluctuation rate equal to 2.6MHz in a longitudinal field of 16G.