Magnetic and dynamical properties in the diluted spin ice Dy2−xLaxTi2O7

We have studied the evolution of the magnetic and dynamical properties as well as structural properties of diluted spin ice Dy2−xLaxTi2O7, where Dy was partially replaced by nonmagnetic La. It is found from Raman spectra that the anomalous phonons should be originated from the strong phonon-phonon anharmonic interaction in the system. Magnetic measurements show that the substitution of La3+ in Dy2Ti2O7 weakens ferromagnetic coupling between Dy-Dy ions, leading to the relaxation of spin ice state. Dynamical properties show that the change of local environment affects the crystal field level, which subsequently determines the energy barriers. We also demonstrate a statistical distribution of relaxation times and an acceleration of spin dynamics near 16 K. The distribution of relaxation times originates from some short-range ordered ferromagnetic glasses/clusters in the process of spin freezing. The vacancies introduced by magnetic dilution make reversing of spins more convenient, resulting in a faster relaxation processes.