Metal/insulator nanogranular material and thin-film magnetic sensor

The present invention provides a metal/insulator nanogranular material including: ferromagnetic particles having a composition represented by the formula (1) (Fe1-xCox)100-z(B1-ySiy)z (1) in which x, y and z each satisfy 0<=x<=1, 0<=y<=1, and 0ferromagnetic particles.