Measurements in Voigt configuration on PLD grown NiO thin films

NiO has great potential applications in gas sensors, optical fibers, solar thermal absorbers, or in non-volatile resistive random memories. In our study NiO, NiMnO, and NiMnLiO have been grown on double-side polished r-plane sapphire substrates by pulsed laser deposition. In contrast to the antiferromagnetic behaviour of bulk NiO, we probed weak ferromagnetism with a coercivity ranging between 150 and 250 Oe by means of SQUID magnetometry. We measured the complex Voigt angle using a HeCd laser, a Glan Taylor polarizer, a Hinds PEM-100 and two LockIns. The polarization state of light after transmission through a sample consisting of ca. 1 μm thick, weak ferromagnetic and diamagnetic NiO thin films on diamagnetic r-plane sapphire substrates has been modelled using the 4*4 matrix formalism in dependence of an external magnetic field applied in-plane. 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 ±0.1 T to a flat-top shape in agreement with the experimentally determined Voigt angle.