Sprayed Nanometer-Thick Hard-Magnetic Coatings with Strong Perpendicular Anisotropy for Data Storage Applications

Abstract

The rapid growth of digital information in the world necessitates a big leap in improving the existing technologies for magnetic recording. For the best modern perpendicular recording, the highest coercivity materials with minimal volume are required. We present a study of a facile technology for establishing mono- and multilayer surfaces from various single-domain flat magnetic nanoparticles that exhibit a strong perpendicular-oriented magnetic moment on solid and flexible substrates. Surfactant-free, hard ferromagnetic, and single-domain anisotropic strontium hexaferrite SrFe12O19 nanoparticles with a perpendicular magnetic moment orientation and two different aspect ratios are self-ordered into magnetic thin nanofilms, exploiting the templating effect of cellulose nanofibrils and magnetic fields. Uniform magnetic coatings obtained by the scalable layer-by-layer spray deposition from a monolayer coverage up to thicknesses of a few tens of nanometers show a preferred in-plane orientation of the hard-magnetic nanoparticles. High coercivities of the films of up to 5 kOe and a high perpendicular anisotropy of M r⊥/M s > 80% are found. The application of the magnetic field during film deposition ensures additional improvement in perpendicular magnetic anisotropy and the appearance of residual magnetization in the film of up to 0.6M s. For low-aspect-ratio nanoparticles stacked in periodic planar structures, the signs of the photonic band gap are revealed. The ability to create scalable, thin magnetic structures based on nanosized particles/building blocks opens great opportunities for their application in a wide variety of optoelectronic and magnetic storage devices.

Means of control over poly(4-vinylpyridine)–CoBr2 complex functional thin film formation in static and dynamic conditions

“…1 The synthesis and deposition are traditionally done separately, contrary to the discussed material where the polymer acts as both the surface and the ligand building the SIM. 2 It is worth mentioning that advancements in obtaining high-density data storage are not limited to molecular magnets, and are also done using magnetic nanoparticles made from hard magnetic materials; 3 however, our method concentrates on chemisorption rather than physisorption, utilizes the substrate as the ligand building the magnetic unit and shows the potential to be applied on a single-ion level.…”