Magnetic properties of Fe_3O_4 thin films grown on different substrates by laser ablation

摘要

Magnetite thin films have been grown onto (100)Si, (100)GaAs and (0001)Al_2O_3, at substrate temperatures varying from 473 to 673 K, by UV pulsed laser ablation of Fe_3O_4 targets in reactive atmospheres of O_2 and Ar, at working pressure of 8 x 10~(-2) Pa. The influence of the substrate on stoichiometry, microstructure and the magnetic properties has been studied by X-ray diffraction (XRD), conversion electron Moessbauer spectroscopy (CEMS) and magnetic measurements. Magnetite crystallites, with stoichiometry varying from Fe_(2.95)O_4 to Fe_(2.99)O_4, are randomly oriented for (100)GaAs and (100)Si substrates and exhibit (111) texture if grown onto (0001)Al_2O_3. Interfacial Fe~(3+) diffusion, which is virtually absent for (100)Si substrates, was found for both (0001)Al_2O_3 and (100)GaAs, with some deleterious effect on the subsequent microstructure and magnetic behaviour.