arXiv subjects

Movaffaq Kateb

Publications and source records attributed to Movaffaq Kateb.

21 records · Page 2Linked to original sources

arXiv2019

Comparison of magnetic and structural properties of permalloy Ni80Fe20 grown by dc and high power impulse magnetron sputtering

We study the microstructure and magnetic properties of Ni80Fe20 thin films grown by high power impulse magnetron sputtering (HiPIMS), and compare with films grown by dc magnetron sputtering (dcMS). The films were grown under a tilt angle of 35° to identical thickness of 37 nm using both techniques, at different pressure (0.13-0.73 Pa) and substrate temperature (room temperature and 100 °C). All of our films display effective in-plane uniaxial anisotropy with square easy axis and linear hard axis magnetization traces. X-ray diffraction reveals that there is very little change in grain size within the pressure and temperature ranges explored. However, variations in film density, obtained by X-ray reflectivity measurements, with pressure have a significant effect on magnetic properties such as anisotropy field (Hk) and coercivity (Hc). Depositions where adatom energy is high produce dense films, while low adatom energy results in void-rich films with higher Hk and Hc. The latter applies to our dcMS deposited films at room temperature and high pressure. However, the HiPIMS deposition method gives higher adatom energy than the dcMS and results in dense films with low Hk and Hc. The surface roughness is found to increase with increased pressure, in all cases, however it showed negligible contribution to the increase in Hk and Hc.

cond-mat.mtrl-sci↗

arXiv2019

Effect of atomic ordering on the magnetic anisotropy of single crystal Ni80Fe20

We investigate the effect of atomic ordering on the magnetic anisotropy of Ni80Fe20 at.% (Py). To this end, Py films were grown epitaxially on MgO (001) using dc magnetron sputtering (dcMS) and high power impulse magnetron sputtering (HiPIMS). Aside from twin boundaries observed in the latter case, both methods present high quality single crystals with cube-on-cube epitaxial relationship as verified by the polar mapping of important crystal planes. However, X-ray diffraction results indicate higher order for the dcMS deposited film towards L12 Ni3Fe superlattice. This difference can be understood by the very high deposition rate of HiPIMS during each pulse which suppresses adatom mobility and ordering. We show that the dcMS deposited film presents biaxial anisotropy while HiPIMS deposition gives well defined uniaxial anisotropy. Thus, higher order achieved in the dcMS deposition behaves as predicted by magnetocrystalline anisotropy i.e. easy axis along the [111] direction that forced in the plane along the [110] direction due to shape anisotropy. The uniaxial behaviour in HiPIMS deposited film then can be explained by pair ordering or more recent localized composition non-uniformity theories. Further, we studied magnetoresistance of the films along the [100] directions using an extended van der Pauw method. We find that the electrical resistivities of the dcMS deposited film are lower than in their HiPIMS counterparts verifying the higher order in the dcMS case.

cond-mat.mtrl-sci↗

arXiv2018

Application of an extended van der Pauw method to anisotropic magnetoresistance measurements of ferromagnetic films

We demonstrate anisotropic resistivity measurements using the extended van der Pauw (vdP) method in ferromagnetic Ni80Fe20 (Py) films. We apply it to measure anisotropic magnetoresistance (AMR) and compare the results of the vdP method with the more conventional Hall-bar method along the hard and easy axis of the film and show that the vdP method gives more reliable AMR result. For instance, the AMR result along the hard and easy axis of the film are in close agreement. Further, we applied the vdP method to study AMR in a series of Py films with thicknesses ranging between 10-250 nm. The films were grown by sputtering deposition at an angle with respect to the substrate normal and with an in-situ magnetic field, both conditions assisting in the definition of in-plane uniaxial anisotropy. The microstructure of Py films was characterized using X-ray reflectivity, diffraction and polar mapping of (111) planes. We detected no off-normal texture and negligible surface roughness, which indicates that self-shadowing is not dominating in our growth. Yet the films have well defined uniaxial anisotropy. Abrupt changes in the average resistivity vs. film thickness were observed, which cannot be explained by the models accounting for the thickness and grain size but strongly correlate with the changes in (111) texture in the films. We compared our results with the literature and show that independent of growth method, substrate and deposition temperature, the AMR value presents a saturation behavior with thickness at about 100 nm.

cond-mat.mtrl-sci↗