Voigt effect measurements on PLD grown nickel oxide thin films

NiO has great potential applications in spin valves, magnetooptical sensors, optical fibers, solar thermal absorbers, or in non-volatile resistive random memories [1]. In our study NiO, NiMnO, and NiMnLiO thin films have been grown on double-side polished r-plane sapphire substrates by pulsed laser deposition. We measured the complex Voigt angle using the polarized light from a HeCd laser, a Glan Taylor polarizer, a Hinds PEM-100 and two LockIns [2]. The Voigt effect is a second-order magneto-optic effect [3]. The polarization state of light after transmission through a sample consisting of ca. 1 μm thick, weak ferromagnetic and diamagnetic NiO thin films on purely diamagnetic r-plane sapphire substrates has been modelled using the 4x4 matrix formalism [2] in dependence of an external magnetic field applied in-plane, i.e. in Voigt configuration. The modelling results revealed that for the bare diamagnetic substrate the Voigt angle depends parabolically on the external magnetic field and that the weak ferromagnetic and diamagnetic NiO thin films changed the parabolic dependence of the Voigt angle in the range of ±0.3 T to a flat-top shape in agreement with the experimentally determined Voigt angle. Furthermore, due to the NiO thin films the Voigt angle increased ca. (1±i)10^-5 deg for an external in-plane field of ±0.3 T.
[1] U. Russo, D. Ielmini, A.L. Lacaita, A. Pirovano, F. Pellizer and R. Bez, IEEE Electron Device Lett. 25 (2004) 507-509.
[2] C. Scarlat, K. M. Mok, S. Zhou, M. Vinnichenko, M. Lorenz, M. Grundmann, M. Helm, M. Schubert, H. Schmidt, Phys. Stat. Sol. (C) 7 (2010) 334-337.
[3] R. Carey and B.W.J. Thomas, J. Phys.: D: Appl. Phys. 7 (1974) 2362-2368.