Magnetic field generator, magnetic sensor system and magnetic sensor

1. A magnetic field generator comprising a plurality of magnetic field generation units arranged in a predetermined pattern to generate a plurality of external magnetic fields, wherein

each of the plurality of magnetic field generation units includes a first ferromagnetic material section and a first antiferromagnetic material section,

the first antiferromagnetic material section is in contact with and exchange-coupled to the first ferromagnetic material section,

the first ferromagnetic material section has an overall magnetization, and

the plurality of magnetic field generation units includes first and second magnetic field generation units configured so that the overall magnetization of the first ferromagnetic material section of the first magnetic field generation unit is in a different direction from the overall magnetization of the first ferromagnetic material section of the second magnetic field generation unit.

2. The magnetic field generator according to claim 1 , wherein

the first ferromagnetic material section includes a plurality of constituent layers stacked on each other, and

the plurality of constituent layers include a first ferromagnetic layer in contact with the first antiferromagnetic material section.

3. The magnetic field generator according to claim 2 , wherein the plurality of constituent layers further include a second ferromagnetic layer which is located farther from the first antiferromagnetic material section than the first ferromagnetic layer.

4. The magnetic field generator according to claim 3 , wherein the plurality of constituent layers further include a nonmagnetic layer interposed between the first ferromagnetic layer and the second ferromagnetic layer.

5. The magnetic field generator according to claim 4 , wherein

the first ferromagnetic layer and the second ferromagnetic layer are ferromagnetically exchange-coupled to each other via the nonmagnetic layer, and

each of the first ferromagnetic layer and the second ferromagnetic layer has a magnetization in the same direction as the overall magnetization of the first ferromagnetic material section.

6. The magnetic field generator according to claim 4 , wherein

the first ferromagnetic layer and the second ferromagnetic layer are antiferromagnetically exchange-coupled to each other via the nonmagnetic layer, and

the second ferromagnetic layer has a magnetization in the same direction as the overall magnetization of the first ferromagnetic material section.

7. The magnetic field generator according to claim 1 , wherein

the first ferromagnetic material section has a first surface and a second surface opposite to each other,

the first antiferromagnetic material section is in contact with the first surface of the first ferromagnetic material section, and

each of the plurality of magnetic field generation units further includes a second antiferromagnetic material section in contact with the second surface of the first ferromagnetic material section and exchange-coupled to the first ferromagnetic material section.

8. The magnetic field generator according to claim 7 , wherein the first and second antiferromagnetic material sections have different blocking temperatures.

9. The magnetic field generator according to claim 1 , wherein

the first antiferromagnetic material section has a first surface and a second surface opposite to each other,

the first ferromagnetic material section is in contact with the first surface of the first antiferromagnetic material section,

each of the plurality of magnetic field generation units further includes a second ferromagnetic material section in contact with the second surface of the first antiferromagnetic material section and exchange-coupled to the first antiferromagnetic material section, and

the second ferromagnetic material section has an overall magnetization.

10. A magnetic sensor system comprising a scale and a magnetic sensor arranged in a variable relative positional relationship with each other, the magnetic sensor system being configured to detect a physical quantity associated with the relative positional relationship between the scale and the magnetic sensor, wherein

the scale is formed of a magnetic field generator,

the magnetic field generator includes a plurality of magnetic field generation units arranged in a predetermined pattern to generate a plurality of external magnetic fields,

each of the plurality of magnetic field generation units includes a first ferromagnetic material section and a first antiferromagnetic material section,

the first antiferromagnetic material section is in contact with and exchange-coupled to the first ferromagnetic material section,

the first ferromagnetic material section has an overall magnetization, and

the plurality of magnetic field generation units includes first and second magnetic field generation units configured so that the overall magnetization of the first ferromagnetic material section of the first magnetic field generation unit is in a different direction from the overall magnetization of the first ferromagnetic material section of the second magnetic field generation unit.

11. The magnetic sensor system according to claim 10 , wherein

the plurality of magnetic field generation units are arranged in a row, and

any two adjacent ones of the plurality of magnetic field generation units are configured so that the overall magnetizations of their respective first ferromagnetic material sections are in different directions from each other.

12. The magnetic sensor system according to claim 11 , wherein the direction of the overall magnetization of the first ferromagnetic material section of one of the two adjacent magnetic field generation units and the direction of the overall magnetization of the first ferromagnetic material section of the other of the two adjacent magnetic field generation units intersect a direction in which the row of the plurality of magnetic field generation units extends and are opposite to each other.

13. The magnetic sensor system according to claim 10 , wherein

the plurality of magnetic field generation units are annularly arranged to form an aggregation having an outer periphery and an inner periphery, and

any two adjacent ones of the plurality of magnetic field generation units are configured so that the overall magnetizations of their respective first ferromagnetic material sections are in different directions from each other.

14. The magnetic sensor system according to claim 13 , wherein the overall magnetization of the first ferromagnetic material section of one of the two adjacent magnetic field generation units is in a direction from the outer periphery to the inner periphery, and the overall magnetization of the first ferromagnetic material section of the other of the two adjacent magnetic field generation units is in a direction from the inner periphery to the outer periphery.

15. A magnetic sensor comprising:

a plurality of magnetic detection elements for detecting a magnetic field to be detected; and

a bias magnetic field generator for generating a plurality of bias magnetic fields to be applied to the plurality of magnetic detection elements, wherein

the bias magnetic field generator is formed of a magnetic field generator,

the magnetic field generator includes a plurality of magnetic field generation units arranged in a predetermined pattern to generate a plurality of external magnetic fields,

each of the plurality of magnetic field generation units includes a first ferromagnetic material section and a first antiferromagnetic material section,

the first antiferromagnetic material section is in contact with and exchange-coupled to the first ferromagnetic material section,

the first ferromagnetic material section has an overall magnetization,

the plurality of magnetic field generation units includes first and second magnetic field generation units configured so that the overall magnetization of the first ferromagnetic material section of the first magnetic field generation unit is in a different direction from the overall magnetization of the first ferromagnetic material section of the second magnetic field generation unit, and

each of the plurality of bias magnetic fields results from the overall magnetization of the first ferromagnetic material section of at least one of the plurality of magnetic field generation units.

16. The magnetic sensor according to claim 15 , wherein each of the plurality of magnetic detection elements is a magnetoresistance element.

17. The magnetic sensor according to claim 16 , wherein the magnetoresistance element includes: a magnetization pinned layer having a magnetization pinned in a certain direction; a free layer having a magnetization that varies depending on the magnetic field to be detected; and a nonmagnetic layer located between the magnetization pinned layer and the free layer.

18. The magnetic sensor according to claim 17 , wherein the overall magnetization of the first ferromagnetic material section of any one of the plurality of magnetic field generation units is in a direction intersecting the direction of the magnetization of the magnetization pinned layer of a specific magnetoresistance element that is to be subjected to a bias magnetic field resulting from the overall magnetization of the first ferromagnetic material section of the one of the plurality of magnetic field generation units.

19. The magnetic sensor according to claim 15 , wherein

the plurality of magnetic detection elements include a first magnetic detection element and a second magnetic detection element connected in series,

the plurality of magnetic field generation units include a first magnetic field generation unit and a second magnetic field generation unit,

a bias magnetic field to be applied to the first magnetic detection element results from the overall magnetization of the first ferromagnetic material section of the first magnetic field generation unit,

a bias magnetic field to be applied to the second magnetic detection element results from the overall magnetization of the first ferromagnetic material section of the second magnetic field generation unit, and

the first and second magnetic field generation units are configured so that the overall magnetizations of their respective first ferromagnetic material sections are in different directions from each other.

20. The magnetic sensor according to claim 15 , wherein

the plurality of magnetic detection elements includes a first magnetic detection element and a second magnetic detection element connected in series,

the plurality of magnetic field generation units includes a first to a fourth magnetic field generation unit,

a bias magnetic field to be applied to the first magnetic detection element results from the overall magnetization of the first ferromagnetic material section of the first magnetic field generation unit and the overall magnetization of the first ferromagnetic material section of the second magnetic field generation unit,

a bias magnetic field to be applied to the second magnetic detection element results from the overall magnetization of the first ferromagnetic material section of the third magnetic field generation unit and the overall magnetization of the first ferromagnetic material section of the fourth magnetic field generation unit,

the first and third magnetic field generation units are adjacent to each other and configured so that the overall magnetizations of their respective first ferromagnetic material sections are in different directions from each other, and

the second and fourth magnetic field generation units are adjacent to each other and configured so that the overall magnetizations of their respective first ferromagnetic material sections are in different directions from each other.