  We investigated the magnetic anisotropy ratio of thin sputtered
polycrystalline MgB2 films on MgO substrates. Using high magnetic field
measurements, we estimated an anisotropy ratio of 1.35 for T=0 K with an upper
critical field of 31.74 T in the parallel case and 23.5 T in the perpendicular
case. Direct measurements of a magnetic-field sweep at 4.2 K show a linear
behavior, confirmed by a linear fit for magnetic fields perpendicular to the
film plane. Furthermore, we observed a change of up to 12% of the anisotropy
ratio in dependence of the film thickness.
