Switching of magnetic easy-axis using crystal orientation for large perpendicular coercivity in CoFe2O4 thin film

Abstract

Perpendicular magnetization and precise control over the magnetic easy axis in magnetic thin film is necessary for a variety of applications, particularly in magnetic recording media. A strong (111) orientation is successfully achieved in the CoFe2O4 (CFO) thin film at relatively low substrate temperature of 100 °C, whereas the (311)-preferred randomly oriented CFO is prepared at room temperature by the DC magnetron sputtering technique. The oxygen-deficient porous CFO film after post-annealing gives rise to compressive strain perpendicular to the film surface, which induces large perpendicular coercivity. We observe the coercivity of 11.3 kOe in the 40-nm CFO thin film, which is the highest perpendicular coercivity ever achieved on an amorphous SiO2/Si substrate. The present approach can guide the systematic tuning of the magnetic easy axis and coercivity in the desired direction with respect to crystal orientation in the nanoscale regime. Importantly, this can be achieved on virtually any type of substrate.

Structural, magnetic and magneto-optical studies of Mn/Al bilayer thin films on GaAs substrates

“…Mn and Al atoms were arranged in a tetragonal distorted s-phase structure aer annealing the as-deposited Mn/Al bilayer lms at 400 C and 500 C. It has been reported in literature that the 3-phase was transformed into the s-phase by annealing the MnAl thin lm below 500 C. 29 The enhancement of the s-phase in the annealed lms could be due to the mixing of the Mn and Al layers at higher temperatures by the diffusion of Mn and Al atoms. The in-plane and out-of-plane strains (3) were calculated by using the formula 3 ¼ (a À a 0 )/a 0 , 30 where 'a' is either the in-plane (a) or out-of-plane (c) lattice parameters, and a 0 is the bulk unstressed lattice parameter for MnAl. Films annealed at 500 C showed the highest out-of-plane compressive strain (3 t ) of À0.084% and an in-plane tensile strain (3 k ) of 0.018%.…”

Epitaxial integration of CoFe2O4 thin films on Si (001) surfaces using TiN buffer layers

“…The very well-known existence of unresolved multiplet splitting can affect strongly the final result. The O1s spectra of both bilayers have been fitted in terms of three symmetrical peaks at 529.9, 531.3 and 532.4 eV which we associate to oxygen in the oxygen lattice bonded to Fe and Co, surface hydroxyl (Fe and Co bonded to OH) and absorbed H 2 O at the surface, respectively [36]. The binding energies of the different contributions appear at the same position for both bilayers and the contribution of the oxygen at the lattice accounts ≈ 80% of the total O 1s area.…”

Effect of surface pinning on magnetic nanostuctures

“…The unusual magnetic properties observed in all these different structures owes to their mesoscopic scale, where size and shape-anisotropy play an important role. It is known that the change in preferential orientation of magnetic easy-axis is responsible for changing the value of coercivity [33]. The microscopic origin of the exchange bias however depends on many details, like the thickness of core and shell [34], anisotropic spin interaction [35] and interaction in the core-shell interface [36].…”