Study of dependence upon the magnetic field and transport current of the magnetoresistive effect in YBCO-based bulk composites

The magnetoresistive properties of bulk YBCO + CuO and YBCO + BaPb0.75Sn0.25O3 composites for different orientations of external magnetic field H and macroscopic transport current j have been measured. These composites exhibit large magnetoresistance in weak magnetic fields (< 100 Oe), which makes them promising candidates for practical application in magnetic field sensor devices. The difference between.( T) dependences, magnetoresistance curves R( H) and current - voltage characteristics measured for H parallel to j and H || j is observed indicating the presence of the Lorentz- force- dependent dissipation in the composites. Angular dependences of magnetoresistance R(theta) ( where theta = angle H, j) of the composites in weak magnetic fields are found to be proportional to sin(2)theta. This fact suggests that the flux flow in the intergrain boundaries is responsible for the large magnetoresistive effect observed in the composites.