Giant Spontaneous Hall Effect and Magnetoresistance in La 1 _ ,

Results of resistivity and Hall effect measurements in Lal_.Ca.Co03 (0.1< z <0,5) epitaxkd films and ceramics are presented. The spontaneous Hall effect in Lal_ZCasCo03 (LCCO) is observed for ferromagnetic samples with z ~0.2. The Hall effect is largest near the magnetic percolation threshold z=O.2. For 2=0.2, tains a large value may be applied to the Iow-field slope of the Hall resistivity, PZV/(PO~), atof 2x 10-6m3/C below the Curie temperature TC, which sensitive low-field detection. Except near the magnetic percolation threshold, the longitudinal resistivity of LCCO decreases with increasing field at all temperatures. Anomalous temperature-dependent magnetoresistance occurs in the sample with z=O.2, which may be associated with the spin-state transition in LCCO.