Magnetic properties of amorphous Bi2DyFe5O12

Amorphous Bi2DyFe5O12 films have been prepared by rf sputtering technique. The magnetic properties, structure and effect of annealing have been investigated. The magnetization increases with increasing magnetic field and is not saturated at a high magnetic field of 65 kOe. In the temperature range 20 K < T < 200 K the susceptibility can be described by a Curie-Weiss law with a Weiss constant of θ = -15 K. The effective paramagnetic moment for the iron ion (4.1 μB) is much smaller than the theoretical moment (5.9 μB). Above 200 K the slope in χ-1 vs T curve changes. The Weiss constant and effective paramagnetic moment for the iron ion increase. After annealing above 600 C the amorphous samples crystallize to a single garnet phase with the magnetization of 21 emu/g at 1.5 K and 7.2 emu/g at 300 K, which are the same as those of the bulk Bi2DyFe5O12 garnet ferrites. (orig.)