Magnetic device and magnetic sensor using the same

A magnetic material sensor comprising:

• a tunnel junction member having a resonant tunnel structure including first and second barrier layers and a quantum well layer interposed between said first and second barrier layers and consisting of a first magnetic film;
• an electron collecting section connected to one surface of said tunnel junction member;
• an electron injecting section connected to the other surface of said tunnel junction member, said electron injecting section including a second magnetic film having a coercive force lower than a coercive force of said first magnetic film;
• a power supply for applying a voltage to said electron injecting section;
• and
• means for detecting a current flowing out from said electron collecting section,
• wherein when a relationship between magnetization directions in said first and second magnetic films is changed by an external magnetic field, the current flowing out from said electron collecting section changes accordingly, and the external magnetic field is sensed on the basis of the change in the current.