Nanostructure of giant magnetoresistive oxide film Nd_⅔Sr_1/3MnO₃ by scanning tunneling microscopy

Abstract

Scanning tunneling microscopy was used to study the surface nanostructure of the epitaxial film Nd_⅔Sr_1/3MnO₃ that shows giant magnetoresistance. The surface morphology of the film consists of a number of overlapping platelets of about 30-35 Å diameter that grow at an angle of 35°-45° to the surface normal. The peak to peak height of the platelets are multiples of the c-axis lattice parameter of 7.85 Å showing that the growth of the platelets takes place by the layer by layer addition of one formula unit. The mean surface roughness is about 10 Å. In the range of a few microns the film exhibits no defects or dislocations. The film is unstable in ambient atmosphere and tends to get covered by an adsorbate layer. Tip-surface interactions cause the adsorbate to be dislodged exposing the surface nanostructure. The degradation of the film in real time when imaged in air was recorded. The adsorbates increase the surface roughness of the film.