| US 7,456,758 B2 | ||
| Magnetic encoder apparatus | ||
| Hiroyuki Hoshiya, Odawara (Japan); Kenichi Meguro, Kaisei (Japan); Kazuhiro Nakamoto, Ninomiya (Japan); and Yasunori Abe, Moka (Japan) | ||
| Assigned to Hitachi Metals, Ltd., Tokyo (Japan) | ||
| Filed on Feb. 20, 2007, as Appl. No. 11/676,608. | ||
| Claims priority of application No. 2006-252928 (JP), filed on Sep. 19, 2006. | ||
| Prior Publication US 2008/0068007 A1, Mar. 20, 2008 | ||
| Int. Cl. H03M 1/22 (2006.01) | ||
| U.S. Cl. 341—15 | 7 Claims |
| 1. A magnetic encoder, comprising:
a magnetic medium on which an area with the width of λa magnetized in a first direction and an area with the width of λb magnetized
in a second direction are alternately disposed; and
a magnetoresistive sensor formed by arranging a plurality of sensor units at intervals in a width direction of the area, each
of the sensor units being formed of a magnetoresistive film patterned into a strip-like shape, the magnetoresistive film having
a structure in which a soft magnetic free layer, a non-magnetic intermediate layer and a ferromagnetic pinned layer are stacked,
a magnetization direction of the soft magnetic free layer changing in response to an external magnetic field,
wherein the soft magnetic free layer of the sensor units has a structure in which a first soft magnetic film, an anti-parallel
coupling film and a second soft magnetic film are stacked in sequential order from a side of the non-magnetic intermediate
layer; and magnetizations of the first soft magnetic film and the second soft magnetic film are magnetically coupled to each
other in anti-parallel directions, and
the magnetic encoder outputs an electric signal having a period of λ=(λa+λb)/2.
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