The use of single‐level circuit has simplified the fabrication process. A thick film detector, however, has weak points; it has a low detection efficiency due to the large demagnetizing field and unfavorable noise is inherent in it. The authors study the magnetoresistive characteristics of permalloy films and find out the detectors with high senstitivity, selecting the appropriate evaporation conditions. The significant results are as follows. (1) The large detection voltage is obtained from those elements whose magnetic easy axis deviates from the shape anisotropy direction, which serves to reduce the effective anisotropy field. (2) This angle of deviation α is increased with the raising of the substrate temperature and with the lowering of the evaporation rate. For example, α=60° at 310°C, 3ÅC, 3Å/sec, and α=0° at 250°C, 10Å/sec. (3) Detection performances are investigated on the 30‐column serpentine detector using 3 μm stripe domain width of (YGdYb)3(GaFe)5012 with a 4π Ms of 260 Gauss. The signal voltage of 1 mV/3 mA and S/N ratio of 5 are obtained at 100 kHz.