Search

Alloying antiferromagnetic Cr with ferromagnetic Ni forms an excellent starting point to design materials for various room temperature applications, such as spintronics, the magnetocaloric effect, and hyperthermia, thanks to its tunable Curie temperature, TC, and competing magnetic interactions. In this report, we present a comprehensive analysis of the relationships among film thickness, Cr surface segregation, and magnetic properties in nanocrystalline Ni100–xCrx (x = 5–15 at. %) thin films. We assess the impact of Cr segregation evolution on various magnetic transitions as the thickness and Cr doping level increase. These films exhibited ferromagnetic to paramagnetic transitions at higher temperatures and ferromagnetic to spin-glass transitions at low temperatures, which resulted in a phase diagram that differed from the bulk equilibrium phase diagram. Further, magnetometry and magnetic force microscopy were performed to investigate the magnetic anisotropy and magnetic domain structure as a function of film thickness. It is found that the perpendicular component of magnetic anisotropy (Q=Kp/(2πMs2)≈0.5) led to a stripe domain structure in films with critical thicknesses above 20 nm. Substantial changes in the magnetization behavior of nanocrystalline Ni100–xCrx thin films within a few Cr at. % doping provide a means for adjusting both soft and hard magnetic component applications. [ABSTRACT FROM AUTHOR]

• Fabrication of SrFe 12 O 19 /α-Fe 2 O 3 or SrFe 12 O 19 /γ-Fe 2 O 3 nanocomposite thin films. • Substantial coercivities (∼5.8 kOe) achieved without high-temperature processing. • Strain-induced shifting of the Morin transition of α-Fe 2 O 3. • Simultaneous hard and soft magnetic properties observed at room temperature. 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 SrFe 12 O 19 : one in a vacuum (FM/AFM: SrFe 12 O 19 /α-Fe 2 O 3) and other in an oxygen atmosphere (hard-FM/soft-FM: SrFe 12 O 19 /γ-Fe 2 O 3). 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-Fe 2 O 3 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. [ABSTRACT FROM AUTHOR]