Magnetic Susceptibility of a Nanocomposite Based on an Opal Matrix with Yb₂Ti₂O₇ Particles

The DC and AC magnetic susceptibilities of an opal matrix-based nanocomposite with pyrochlore-structured ytterbium titanate particles up to 60 nm in size have been studied in the range of magnetic fields up to 30 kOe. The measurements were performed at temperatures from 2 to 200 K. The temperature dependence of the nanocomposite Yb₂Ti₂O₇ has been found to deviate significantly from the Curie–Weiss law. From the frequency dependence of the AC susceptibility measured in the range from 10 Hz to 10 kHz, the spin relaxation times have been determined, and two relaxation times have been found to be required for the description of the frequency dependence of the susceptibility. The field dependence of the AC susceptibility has been measured. This dependence is proved to be described by the modified Cole–Cole formula. The characteristic fields of the magnetic field dependence of the real part of the susceptibility are determined, the value of the characteristic field being found to increase with increasing temperatures.