ORALS

SESSION: AdvancedMaterialsWedPM1-R8	4th Intl. Symp. on New and Advanced Materials and Technologies for Energy, Environment and Sustainable Development
Wed Nov, 7 2018 / Room: Grego (50/3rd)
Session Chairs: Yashika Gupta; Jarugu Narasimha Moorthy; Session Monitor: TBA

15:15: [AdvancedMaterialsWedPM108]
Heusler Alloy Thin Films Fabricated by DC Magnetron Co-sputtering
Jan Lancok¹ ; Stanislav Cichon² ; Katerina Horakova² ; Vladimir Chab² ; ¹Institute of Physics ASCR, Prague 8, Czech Republic; ²Institute of Physics ASCR, Prague, Czech Republic;
Paper Id: 257 [Abstract]

Heusler compounds have composition XYZ (so called half-Heuslers) or X₂YZ (so called full-Heusler). Their tuneability originates from large number of elements. This provides the opportunity to adjust electronic structure and hence material properties in many desired directions, such as: half-metallic material for spintronic applications, zero-gap topological semiconductors etc [1]. The properties of Heusler alloys are very sensitive to any non-stoichiometry and crystalline defect. Due to this, in our work we presented the fabrication of the thin films by DC magnetron sputtering in Ar gas by co-sputtering from three single elements targets with independent controlled powers supplies, when the film composition was controlled by DC power. Depositions were carried out in an UHV vacuum chamber evacuated before deposition to pressure 5x10^-8 Pa. The plasma composition and energy of the species were monitored by mass spectroscopy using a Hiden 500 spectrometer. The relation between plasma properties and films structured was carefully examined. The spatial distribution of particular metals were characterised by means of EDX analyses performed at 3 inch Si substrate placed at the same target substrate distance. With this method, we fabricated two different kinds of Heusler alloys (i) magnetic Rh₂MnBi films with high (ii) ultrathin Fe₂ZrSi corrosion protection films. The structural properties of all films were studied by surface techniques such as STM, AFM, and by NanoESCA (Oxford instruments Omicron Nanoscience) instrument, which is based on a PEEM (Photoelectron Emission Microscope) and PES (Photoelecton Spectroscopy). The structural properties were characterized by XRD and SEM equipped by EDX and EDSB techniques. Firstly, the epitaxial Rh-Mn-Bi crystalline films were grown at substrate temperature from RT up to 500 °C on the MgO substrates. Theoretical calculations predict very high magnetic moment for Rh₂MnBi, Ai<i>μ_B</i> = 5 Bohr magnetons per formula unit. Another study reports calculations showing enhanced magneto-optical response of the material. However, in case of the Rh-Mn-Bi system, there is a huge dissimilarity among the metals; a) The melting temperature of Rh reaches 2000 °C b) Although the Mn melting temperature is relatively medium high, 1250 °C, it has a relatively high vapor pressure ; c) Mn oxidizes easily; d) The Bi melting temperature is only 271.4°C, and its vapor pressure is very high, which make the fabrication of these films very difficult. Our attention was focused on the relation of the deposition parameters on the structural and following magnetic properties of the films characterized by vibrating sample magnetometer and by Magneto-optical Kerr effect.<br />Secondly we studied initial stages of Fe and Si atoms interactions with Zr (0001) surface. Ultrathin Fe-Si films were evaporated on the Zr(0001) surface [2]. The formation of the stable corrosion resistance Fe₂ZrSi or FeZrSi Heusler alloys was formed. Following by means of DC magnetron sputtering, the multicomponenct gradient films Fe-Si-Zr from Zr, Fe and Si targets were fabricated on polycrystalline disc Zr (99%) with diameter 12 mm. The depositions were carried out in UHV conditions in pure argon atmosphere at substrate temperature varied from 20-700 °C [3]. Electrochemical Impedance Spectroscopy was employed to analyse the corrosion characterization of Zr with protective Heusler-like films. The effect of Fe-Si-Zr films composition and structure on surface chemistry, morphology, and corrosion behaviour of Zr was examined and evaluated.

References:
[1] T. Graf, S. S. P. Parkin, C. Felser, IEEE Transactions on Magnetics 47 (2011) 367.\n[2] K. Horkova, S. Cichoň, J. Lancok, P. Sajdl, V. Chab , Initial astages of Zr-Fe-Si alloy formation on Zr(0001) surface, Surface Science 657 (2017) 28-34.\n[3] K. Horakova, S. Cichoň, J. Lancok, I. Kratochvilova, L. Fekete, P. Sajdl, A. Krausova, J. Macak, V. Chab, Corrosion protection of zirconium surface based on Heusler alloy Pure and Applied Chemistry 89 (2017) 553-563.