Evatec AG, Hauptstrasse 1a, Trübbach, Switzerland, CEA-LETI/Minatec, 17 rue des Martyrs, Grenoble, Cedex 9, France, Department of Condensed Matter Physics, Masaryk University, Kotlá?ska 2, Brno, Czech Republic, CEITEC, Masaryk University, Kamenice 5, Brno, Czech Republic

"We present an innovative, economical method for manufacturing soft magnetic materials that may pave the way for integrated thin film magnetic cores with dramatically improved properties. Soft magnetic multilayered thin films based on the Fe-28%Co20%B (at.%) and Co-4.5%Ta4%Zr (at.%) amorphous alloys are deposited on 8"" bare Si and Si/200nm-thermal-SiO2 wafers in an industrial, high-throughput Evatec LLS EVO II magnetron sputtering system. The multilayers consist of stacks of alternating 80-nm-thick ferromagnetic layers and 4-nm-thick Al2O3 dielectric interlayers. Since in our dynamic sputter system the substrate cage rotates continuously, such that the substrates face different targets alternatively, each ferromagnetic sublayer in the multilayer consists of a fine structure comprising alternating CoTaZr and FeCoB nanolayers with very sharp interfaces. We adjust the thickness of these individual nanolayers between 0.5 and 1.5 nm by changing the cage rotation speed and the power of each gun, which is an excellent mode to engineer new, composite ferromagnetic materials. Using X-ray reflectometry (XRR) we reveal that the interfaces between the FeCoB and CoTaZr nanolayers are perfectly smooth with roughness of 0.2-0.3 nm. Kerr magnetometry and B-H looper measurements for the as-deposited samples show that the coercivity of these thin films is very low, 0.2-0.3 Oe, and gradually scales up with the thickness of FeCoB nanolayers, i.e. with the increase of the overall Fe content from 0 % (e.g. CoTaZr-based multilayers) to 52 % (e.g. FeCoB-based multilayers). We explain this trend in the random anisotropy model, based on considerations of grain size growth, as revealed by glancing angle X-ray diffraction (GAXRD), but also because of the increase of magnetostriction with the increase of Fe content as shown by B-H looper measurements performed on strained wafers. The unexpected enhancement of the in-plane anisotropy field from 18.3 Oe and 25.8 Oe for the conventional CoTaZr- and FeCoB-based multilayers, respectively, up to ?48 Oe for the nanostructured multilayers with FeCoB/CoTaZr nano-bilayers is explained based on interface anisotropy contribution. These novel soft magnetic multilayers, with enhanced in-plane anisotropy, allow operation at higher frequencies, as revealed by broadband (between 100 MHz and 10 GHz) RF measurements that exhibit a classical Landau-Lifschitz-Gilbert (LLG) behavior. © 2017 Author(s)."

Aluminum compounds, Amorphous alloys, Amorphous films, Amorphous silicon, Anisotropy, Cobalt, Cobalt compounds, Ferromagnetic materials, Ferromagnetism, Film preparation, Grain growth, Interfaces (materials), Magnetic materials, Magnetic multilayers, Magnetism, Silicon wafers, Soft magnetic materials, Substrates, Tantalum compounds, Ternary alloys, Thin films, X ray diffraction, Zirconium compounds, Dielectric interlayers, Ferromagnetic resonance frequency, Glancing angle x-ray diffractions, Magnetron sputtering systems, Multilayered thin films, Nanostructured multilayers, Random anisotropy models, Soft magnetic multilayers, Multilayers