Large magneto-elastic anisotropy enhancement with temperature in composition-graded FeCoTa thin films

Abstract

Static and dynamic magnetic properties of composition-graded FeCoTa thin films were systematically studied with respect to temperature and the deposition power of Ta target. The magnetic anisotropy field and ferromagnetic resonance frequency were found to be increased with the increasing of deposition power of Ta target due to the enhancement of stress when Ta concentration is increased. Thermal stability of the films shows a very interesting behavior with a peculiar and large increasing of magnetic anisotropy with temperature when the deposition power for Ta is moderate while it exhibits normal decreasing with temperature when the deposition power is low or high. The results are discussed and explained in terms of the magneto-elastic anisotropy contribution when the stress of the films is varied.

Electric field control of microwave characteristics in composition-graded FeCoTa film grown onto [Pb(Mg1/3Nb2/3)O3]0.68-[PbTiO3]0.32(011) crystal

“…41,43 Note that the magnetic anisotropy arising from gradient composition sputtering is also of stress-induced origin due to the substitution of larger Ta atoms into Fe or Co sites, which generates a compressive stress along the hard axis. 41 Hence, even without E-field, the composition-graded FeCoTa film already has a large uniaxial magnetic anisotropy which manifests itself as the high f FMR of 7.2 GHz for the unpoled as-deposited sample. It is well known from Kittel's equation that f FMR is related to H K and M S as follows: 41…”

“…Technical details of the gradientcomposition sputtering setup can be found in our previous papers. 41 The stress-induced in-plane uniaxial magnetic anisotropy arising from composition gradient has an easy axis along applied during the deposition to assist the inducement of magnetic anisotropy. A film of Au (100 nm) with a thin Ti buffer layer (10 nm) was deposited on the back side of the substrate as illustrated in Fig.…”

“…Specifically, when an E-field is applied the PMN-PT will generate an anisotropic in-plane stress onto FeCoTa film, which in turn helps inducing the in-plane magnetic anisotropy of the film. The stress-induced uniaxial magnetic anisotropy field H K can be expressed as [41][42][43] …”

“…A vibrating sample magnetometer (VSM) was employed to characterize the static magnetic properties of the sample. We use the shorted micro-strip transmission-line perturbation method 41 with the measured frequency from 0.1 GHz to 10 GHz to characterize the permeability spectra of the sample. During the measurement of the dynamic permeability spectra, a voltage is applied across the thickness of the sample (see Fig.…”

Synthesis, permeability resonance and microwave absorption of flake-assembled cobalt superstructure

“…In recent years, more and more attentions have been focused on the electromagnetic microwave absorption and electromagnetic interference shielding materials [1][2][3][4][5][6][7]. To obtain highefficient microwave absorption materials, there are two key problems to overcome [8].…”