Magnetotransport properties of nano-constriction array in La<Subscript>0.67</Subscript>Sr<Subscript>0.33</Subscript>MnO<Subscript>3</Subscript> film

Nano-constriction array in La<Subscript>0.67</Subscript>Sr<Subscript>0.33</Subscript>MnO<Subscript>3< /Subscript> film was fabricated by using ion beam etching masked by a monolayer of packed and ordered array of SiO<Subscript>2</Subscript> microspheres. Nano-constrictions of around 50 nm in width were fabricated. The low field magnetoresistance (LFMR) exhibited in the samples were observed to be current dependent and the I-V characteristics of the film were found to be nonlinear. These observations were attributed to the co-existence of the ferromagnetic regions and the nano-constricted region of weakened ferromagnetic coupling where Mn<Superscript>3+</Superscript>-O-Mn<Superscript>4+</Superscript> bond were distorted due to the ion beam bombardment. The spin polarized bias current would strengthen local ferromagnetic coupling when passing through this nano-constricted regions. This current effect is relatively large comparing to the external magnetic field to the drop of resistance. Copyright EDP Sciences/Società Italiana di Fisica/Springer-Verlag 2005