Evaluation of Exchange Stiffness From Temperature-Dependent Magnetization in ZnFe2O4 Thin Films

Nano-crystalline magnetic ZnFe
₂
O
₄
thin films were deposited in oxygen atmosphere at different substrate temperatures (T
_S
) on amorphous quartz substrate by pulsed laser deposition technique. The T
_S
= 350 °C film was also annealed at different temperatures in air. X-ray diffraction patterns confirmed that all the samples were cubic spinel and the average grain size of the films increased with increasing T
_S
and annealing temperatures (T
_A
). Spontaneous magnetization at different temperature was obtained from the M-H loops. The temperature dependence of magnetization data was fit using Bloch's law. The value of exchange stiffness constant (D) was calculated using the fit values of Bloch's constant. The obtained D values were found to gradually decrease with the increase of average grain size.