Magnetic anisotropy and high frequency permeability of multilayered nanocomposite FeAlO thin films

Abstract

A cool-down step deposition process (multistep deposition with cool-down interval) was used to grow nanocomposite FeAlO thin films of various thicknesses up to 440nm by magnetron sputtering at a substrate temperature of 15°C. The effect of the number of cool-down steps on the soft magnetic properties and high frequency characteristics of the nanocomposite FeAlO films were investigated. The deposition process was proved very effective in improving the soft magnetic properties and high frequency characteristics of the films. The eight-layered samples, fabricated by eight cool-down step deposition process, of thicknesses of 220 and 440nm had obvious in-plane uniaxial anisotropies while the single-layered films were nearly isotropic. The resulting real permeability value of the eight-layered films was larger than 300 for the 220nm film and between 200 and 300 for the 440nm film.

Soft magnetic properties and high frequency permeability in [CoAlO/oxide] multilayer films

“…The thickness of each magnetic layer was fixed at 35 nm, for it gave good soft magnetic properties and high frequency response in the single layer film. It should be noted that the above single layer films were continuously deposited without suspending the sputtering process while the multilayer films were intermittently deposited with a time interval (>30 min) between the depositions of two neighbouring layers, just like the 'cold-down' deposition method previously employed in the Fe-based films [14]. It was seen that the coercivities reduced quickly on introducing the oxide spacers and reached low stable values of ∼20 and 12 Oe, respectively, for H ce and H ch when t o increased to 2 nm for AlO x or 5 nm for SiO x .…”

“…This is because the thickness changes the microstructures and/or film stress, which would have a great influence on the soft magnetism [7][8][9][10]. Various methods, such as doping, seeding layer or lamination, have been developed to improve the magnetic properties in thick films [11][12][13][14]. Recently, in a series of publications, Beach et al suggested a new kind of soft magnetic films consisting of FeCo-based metallic layers and their native oxides [15].…”

High-frequency permeability spectra of FeCoSiN/Al2O3 laminated films: Tuning of damping by magnetic couplings dependent on the thickness of each ferromagnetic layer

“…This improvement in M-H loops shows that the lamination is effective in obtaining soft magnetic properties in thick films. [4][5][6][7][8] No discrepancy between magnetization processes in different FM layers can be observed. It indicates that the laminated FM layers are either well coupled with each other or have almost the same magnetic properties in each layer.…”

“…1-3 However, the thickness of this kind of granular thin films is usually limited, since the growth of the granular size with the film's thickness will finally lead to the deteriorations of the soft magnetic properties. 4,5 One way to obtain the thick films is to laminate the films with interlayers. [5][6][7][8] Different kinds of materials have been employed as the interlayer, including both ferromagnetic ͑FM͒ 9,10 and nonmagnetic layers, 11,12 both metals 13,14 and insulators.…”

“…26 However, in the study of laminated films, where the FM layer and interlayer repeat periodically, the issue about the magnetic couplings has not been paid enough attention. 4,5 The main reason for this overlook is that the effect of magnetic couplings is often covered up by that from the grain size confinement. Another reason is that the effect of magnetic couplings in laminated films is not as obvious as that in the MTJ or spin valve structure, where the influence is remarkably reflected by the shape and shift of the hysteresis loops.…”