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

Laser ablated zinc ferrite (ZnFe
₂
O
₄
) films deposited at O
₂
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 ZnFe
₂
O
₄
samples display amplitudes somewhat reduced with respect to those in other ferrimagnetic oxides with the exchange coupled Fe
³⁺
pairs, i.e., in Li
_0.5
Fe
_2.5
O
₄
and MgFe
₂
O
₄
spinel ferrite and magnetoplumbite, PbFe
₁₂
O
₁₉
. The lower amplitudes are probably due to the interplay of nanocrystalline nature and lower degree of spinel inversion in the ZnFe
₂
O
₄
laser ablated films.