We fabricated a new magnetic thin film sensor using a large Barkhausen effect. The sensor consists of a Ni-Fe thin film stripe, 0.7 mm by 4.6 mm, on a glass substrate and an aluminum thin film search coil of 400 turns on the other side of the substrate. The Ni-Fe thin film is a bi-layer composed of a soft magnetic layer and a semi-hard magnetic layer. The aluminum thin film search coil size is 6 mm by 10 mm; the line width and space are 5 μm. As a result, the sensor generated an induced pulse of about 1.4 mV by the large Barkhausen jump under asymmetrical ac magnetic fields in the frequency range from 1 to 100 Hz.
