Smart nanocomposite SrFe12O19/α or γ − Fe2O3 thin films with adaptive magnetic properties

Abstract

Ferromagnetic (FM)/antiferromagnetic (AFM) or hard-FM/soft-FM nanocomposites are compelling due to their benefits in future spintronics. We fabricated two distinct nanocomposites thin films by altering the gaseous environment during laser ablation of SrFe12O19: one in a vacuum (FM/AFM: SrFe12O19/α-Fe2O3) and other in an oxygen atmosphere (hard-FM/soft-FM: SrFe12O19/γ-Fe2O3). The in-situ growth and ex-situ annealing temperatures significantly affect the composition of AFM, soft-FM, and hard-FM phases in nanocomposite films. M−H loops show substantial coercivity values (∼5 kOe) in room temperature grown FM/AFM nanocomposites films, while hard-FM/soft-FM nanocomposites films display an exchange spring system with hard (5.8 kOe) and soft (0.16 kOe) magnetic phases. Morin transition of AFM α-Fe2O3 phase is shifted to a lower temperature of around 60 K compared to the bulk value of 260 K, owing to intergranular strain effect, and this has a detrimental effect on FM properties of FM/AFM nanocomposite films. Despite most research focuses on multilayers, the aforementioned unique magnetic properties in FM/AFM and hard-FM/soft-FM nanocomposites thin films hold significant relevance for numerous applications.