Magnetic Relaxation in Ferrimagnetic Glass-Ceramics Obtained by Co-Precipitation at Different Temperatures

Magnetic induction hyperthermia is a promising technique aimed at the treatment of cancer cells; however, the efficiency of the heat release is determined by the magnetic stability of the system. Ferrimagnetic glasses composed of magnetite and hematite crystals in a glassy matrix were prepared by melting of commercial reagents. The time evolution of the magnetic remanence was studied by submitting each sample to a saturating field of 20 kOe for 300 s. After sudden removal of the magnetic field, the evolution of the magnetic remanence was recorded for times up to 5times10⁴ s. In all cases, the remanent magnetization exhibits a nonsaturating, monotonic decrease of its magnitude. The results are interpreted in terms of rearrangements of disordered magnetic volumes at interfaces between adjacent magnetite crystals.