Study of magnetic and multiferroic oxides by scanning force microscope

The first part of this dissertation introduces the techniques for scanning force microscope(SFM) that we use to investigate our samples. A compact design for a low-temperature SFM is presented in the second part. A fiber-optic interferometer is used as cantilever deflection sensor. The tip-sample coarse approach and lateral tip positioning are performed by piezoelectric positioners in situ. The microscope has been operated at temperatures between 6K and 300K and could be incorporated with an 8 Tesla superconducting magnet in out-of-plane direction. Our homemade SFM is also capable of scanning in multi-modes. The second and third part focuse on our results of two different samples: a multiferroic polycrystalline (EuMnO3)0.5(YMnO3)0.5 sample and a colossal magnetoresistive(CMR) manganite La0.60Ca0.40MnO3 thin film grown on NdGaO3(001) substrate.Physic