Reduction in anti-ferromagnetic interactions in ion-beam deposited Fe_3O_4thin films

摘要

Phase pure Fe_3O_4 thin films of thickness ～42nm have been prepared on the Si(100) substrate by reactive ion beam sputtering in the growth temperature range of 150-250 ℃. A high degree of phase purity in the 175 ℃ sample has been confirmed by the XRD, Raman shift, and R-T measurements. The polycrystalline films show a sharp Verway transition as supported by temperature dependent resistivity, AC susceptibility, and coercivity behavior. The significant feature of these films is the early saturation of their room temperature magnetization at ～400 mT, indicating the presence of low anti-ferromagnetic competitions in sharp contrast to most of the previous reports. The noticeable reduction of anti-phase boundaries and its dependence on growth temperature has been correlated with the energetic ion-beam deposition process, and explained in terms of the of ionic vacancy migration approach of Eerenstein et al. [Phys. Rev. B 68, 014428 (2003)]. The electronic conduction of these films is governed by near-neighbor hopping above 240 K and Shklovskii-Efros variable range hopping below this transition temperature.