Ferromagnetism in transition metal doped ZnO

• Antragstellerin: Professorin Dr. Heidemarie Schmidt
• Fachliche Zuordnung: Experimentelle Physik der kondensierten Materie
• Förderung: Förderung von 2006 bis 2010
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 28587221

• Erstellungsjahr: 2012

Zusammenfassung der Projektergebnisse

Camelia Scarlat and Kahming Mok have combined spectroscopic ellipsometry with a 3D vector magnet to extract the optical conductivity tensor of magnetisable materials. These measurements require generalized ellipsometry or Mueller-matrix measurements to observe the off-diagonal elements of the magnetooptical dielectric tensor. Characterization is straightforward if the thin film magnetization is saturated along one of the principal axis of the lab system, which can be accomplished with their special 8-pole vector magnet. We used this 3D vector magnet to study the magneto-optical properties of ferromagnetic iron, nickel, and cobalt thin films. This new technique will help lead future research on the optical conductivity tensor of transparent materials with spin polarized charge carriers, e.g. of transition metal doped ZnO. In the beginning of the project work we were surprised that the complex Kerr angle of iron, nickel, and cobalt thin films with comparable thickness and with comparable saturation magnetization showed different sign at the same wavelength and that the complex Kerr angle of a given metal thin film changed sign in dependence on the wavelength. Finally, we successfully described the off-diagonal elements of the magnetooptical conductivity tensor by products between a wavelength dependent magnetooptical coupling constant and the thin film magnetization. The determined off-diagonal elements of the magnetooptical conductivity tensor well agree with spin-dependent density functional calculations. They are independent of the thin film thickness and allow to predict the magnetooptical response of arbitrary magnetisable multilayer systems for any experimental configuration (wavelength and polarization state of incident light and angle of incidence). This work has been honoured in the Featured researcher article “Heidemarie Schmidt, Ph.D.”, Annual Newsletter J.A. Woollam Co., Inc., 13 (2012) 3.

Projektbezogene Publikationen (Auswahl)

• Mn - implanted, polycrystalline indium tin oxide and indium oxide films. IBMM 2008 - 16th International Conference on Ion Beam Modification of Materials, 31.08.- 05.09.2008, Dresden, Germany, Proceedings: Nuclear Instr. and Methods in Physics Research B 267 (2009) 1616-1619
  Scarlat, C.; Vinnichenko, M.; Xu, Q.; Bürger, D.; Zhou, S.; Kolitsch, A.; Grenzer, J.; Helm, M.; Schmidt, H.
  
• Anisotropic magneto-optical response of metallic thin films probed by Vector-Magneto- Optical Generalized Ellipsometry. Trends in Spintronics and Nanomagnetism (TSN-2010), Lecce, Italy, 24. May 2010
  Mok, K.M.
  
• Voigt effect measurement on PLD grown NiO thin films. 12th International Conference on the Formation of Semiconductor Interfaces (ICFSI-12), 05.- 10.07.2009, Weimar, Germany, Proceedings: phys. stat. sol. (C) 7 (2010) 2, 334-337
  Scarlat, C.; Mok, K. M.; Zhou, S.; Vinnichenko, M.; Lorenz, M.; Grundmann, M.; Helm, M.; Schubert, M.; Schmidt, H.
  
• Dielectric function and magneto-optical Voigt constant of Cu2O: A combined spectroscopic ellipsometry and polar magneto-optical Kerr spectroscopy study. Phys. Rev. B 84 (2011) 195203
  Haidu, F.; Fronk, M.; Gordan, D. O.; Scarlat, C.; Salvan, G.; Zahn, R. T. D.
  
• Functional properties of nickel cobalt oxide thin films. Thin Solid Films 520 (2011) 651 – 655
  Iacomi, F.; Calin, G.; Scarlat, C.; Irimia, C.; Doroftei, M.; Dobromir, G.G.; Rusu, N.; Iftimie, A.V. Sandu
  
• Investigation of the magneto-optical coupling in ferromagnetic thin films by vector-magnetooptical generalized ellipsometry. Phys. Rev. B 84 (2011) 094413
  Mok, K.M.; Kovács, G. J.; McCord, J.; Li, L.; Helm, M. & Schmidt, H.
  
• Thickness independent magneto-optical coupling constant of nickel films in the visible spectral range. J. Appl. Phys. 110 (2011)123110
  Mok, K. M.; Scarlat, C.; Kovacs, György J.; Li, L.; Zviagin, V.; McCord, J.; Helm, M.; Schmidt, H.
  
• Vector-Magneto-Optical Generalized Ellipsometry. Rev. Sci. Instrum. 82 (2011) 033112
  Mok, K. M.; Du, N. & Schmidt, H.
  
• Voigt effect measurements on PLD grown nickel oxide thin films. DPG Spring Meeting of the Condensed Matter Division, 13.-18.03.2011, Dresden, Germany
  Scarlat, C.; Mok, K. M.; Zhou, S.; Lorenz, M.; Grundmann, M.; Helm, M.; Schubert, M.; Schmidt, H.