Variation of magnetic domain structure correlated to low-field magnetoresistance hysteresis in La$_{0.66}$Ca$_{0.34}$MnO$_{3}$ film as observed by magnetic force microscopy.*

The ferromagnetic domain structure of a 150-nm-thick La$_{0.66}$Ca$_{0.34}$MnO$_{3}$ film was imaged by magnetic force microscopy (MFM) as a function of in-plane applied field at 240K, just below T$_{C}$. The film was grown by sputtering on a (001) SrTiO$_{3}$ substrate. The variation of the domain structure is correlated with the hysteresis in both magnetization and magnetoresistance. The resistance peak in the magnetoresistance coincides with the coercivity of the film and sweeping changes in the MFM images. We show the effect of applying the in-plane magnetic field along both in-plane crystalline axes.