Biosensor, method for detecting biomolecules, and biochip

1. A sensor, comprising:

a substrate;

a first magnetoresistance element and a second magnetoresistance element, each of which is a magnetoresistance element whose resistance value measured changes depending on a direction of an input magnetic field; and

a soft magnetic thin film disposed adjacent to the first and second magnetoresistance elements;

wherein one of the first and second magnetoresistance elements is positioned on one of end sides of the soft magnetic thin film and other of the first and second magnetoresistance elements is positioned on other of the end sides of the soft magnetic thin film in a plan view in a direction perpendicular to a film surface of the soft magnetic thin film.

2. The sensor according to claim 1 , wherein the sensor further includes a half bridge circuit configured to detect an operating voltage between connection points.

3. The sensor according to claim 1 , wherein each of the first magnetoresistance element and the second magnetoresistance element is a spin valve type elements having a magnetization fixed layer and a magnetization free layer,

a magnetization fixed direction of the magnetization fixed layer of each of the first and second magnetoresistance elements is: substantially parallel or substantially antiparallel to the leakage magnetic field which is a magnetic field input from an end face of the soft magnetic thin film; and is in a film surface direction of each of the first and second magnetoresistance elements, and

the magnetization fixed direction of the first magnetoresistance element and the magnetization fixed direction of the second magnetoresistance element are substantially parallel to each other.

4. The sensor according to claim 1 , further comprising:

a compensation current line disposed between one of the first and second magnetoresistance elements and the substrate, the compensation current line being configured to apply a compensating magnetic field to the one of the first and second magnetoresistance elements in a direction opposite to a magnetic field applied to the one of the first and second magnetoresistance elements.

5. The sensor according to claim 1 , wherein a main surface of each of the first and second magnetoresistance elements opposite to the substrate and a main surface of the soft magnetic thin film opposite to the substrate are disposed at different positions in the normal direction to the substrate.

6. A biochip comprising the sensor according to claim 1 .