Ellipsometry and magnetooptical Kerr effect study of nanocrystalline zinc ferrite thin films

Laser ablated zinc ferrite (ZnFe₂O₄) films deposited at O₂ pressure of 0.16 mbar onto fused quartz substrates are nanocrystalline and display net magnetic moment dependent on the substrate temperature (T_s) during deposition. At T_s = 350 °C, the room 4πM_s reached the maximum of 3 kG. The films were studied by spectral ellipsometry and magnetooptical (MO) Kerr effect spectroscopy at photon energies between 1 and 5 eV at room temperature in the longitudinal magnetic flux density 1.14 T. The optical and MO spectra show structural details typical for inverted spinels. Our ZnFe₂O₄ samples display amplitudes somewhat reduced with respect to those in other ferrimagnetic oxides with the exchange coupled Fe³⁺ pairs, i.e., in Li_0.5Fe_2.5O₄ and MgFe₂O₄ spinel ferrite and magnetoplumbite, PbFe₁₂O₁₉. The lower amplitudes are probably due to the interplay of nanocrystalline nature and lower degree of spinel inversion in the ZnFe₂O₄ laser ablated films.