A magnetic sensor that includes a magnetic film deposited on a surface acoustic wave device. The surface acoustic wave device includes an input interdigital transducer and an output interdigital transducer. An RF voltage can be applied at the input interdigital transducer in order to generate acoustic waves, which can travel via the magnetic material to the output interdigital transducer. The application of an external magnetic field alters the conductivity of the magnetic material. Such a change in conductivity attenuates the velocity of the traveling surface acoustic wave and an output frequency due to electro acoustic interaction. The change in the applied magnetic field can be indirectly monitored as a change in output frequency of the SAW device at the output interdigital transducer.