New system for measuring magnetic after-effect: application to nickel ferrite

An automatic system for measuring magnetic viscosity in bulk materials based on an inductive technique has been developed. The system allows to study the magnetization variation when the magnetic field is suddenly changed. The system procedure provides a set of isothermal curves in the range 77<T(K)<400. In order to study the temperature dependence of the relaxation phenomena from the isothermal curves, the isochronal spectrum is obtained. Measuring the after-effect of nickel ferrite samples tests the capability of our system. The obtained spectra show a relaxation process between 250 and 350 K. The dependence of this relaxation process on the amplitude of the external magnetic field is also analyzed