Magnetic susceptibility of nanocomposite rare-earth titanates in alternating fields

The magnetic susceptibility of nanocomposite rare-earth titanates has been studied experimentally at low temperatures in the frequency range from 1 to 10 kHz. The studies have been performed on nanocomposites based on opal matrices into interspherical voids of which were incorporated particles of titanates Gd$_{2}$Ti$_{2}$O$_{7}$, Yb$_{2}$Ti$_{2}$O$_{7}$, Dy$_{2}$Ti$_{2}$O$_{7}$ and Dy$_{2}$Si$_{2}$O$_{7}$ with sizes to 60 nm. The frequency dependences of the ac susceptibility of nanocomposites with particles of Gd$_{2}$Ti$_{2}$O$_{7}$, Dy$_{2}$Ti$_{2}$O$_{7}$ and Dy$_{2}$Si$_{2}$O$_{7}$, Yb$_{2}$Ti$_{2}$O$_{7}$, have been measured in the temperature range 2–20 K. At frequencies higher 1 kHz, the frequency dependences of all these nanocomposites is adequately described by the model relaxing oscillators and is approximated by the Debye formula. However, to describe the frequency dependences of the susceptibility from 1 to 10 kHz, a model with two relaxation times is necessary.