TECHNICAL FIELD

The present application relates to a magnetic sensor, and a magnetic encoder provided with the magnetic sensor.

BACKGROUND

Conventionally, in machine tools or the like, a position detecting device for detecting a position created by the rotational movement or linear movement of a movable body is used. One type of known position detecting device is provided with a medium/media where magnetic signals are recorded and a magnetic sensor, and the magnetic sensor can output a signal indicating a relative positional relationship between a medium and the magnetic sensor.

One known magnetic sensor used in such a position detecting device is a multilayer body having a free layer and a magnetization pinned layer and provided with a magnetoresistive effect element (MR element) where resistance is changed in association with a magnetization direction of the free layer according to an external magnetic field. Further, known media used in such a position detecting device include, for example, one having a track for absolute signals, one having a track for incremental signals, one having a track for absolute signals and a track for incremental signals.

Conventionally, one magnetic sensor used for the position detecting device provided with the medium having a track for absolute signals and a track for incremental signals has two types of MR elements: an MR element for detecting a magnetic signal recorded in the track for absolute signals and an MR element for detecting a magnetic signal recorded in the track for incremental signals is proposed (see Patent Literature 1).

Patent Literature

Japanese Patent Application Laid-Open No. 2001-264112

In the magnetic sensor, the MR element for detecting a magnetic signal recorded in the track for absolute signals requires a characteristic (response characteristic) to exponentially change an output in response to the change of the magnetic field relative to the relative movement of the medium. In the meantime, the MR element for detecting a magnetic signal recorded in the track for incremental signals requires a characteristic (response characteristic) to linearly change the output in response to the change of the magnetic field relative to the relative movement of the medium.

Thus, in two types of MR elements with different response characteristics in demand, recently, improvement of the response characteristics, such as further higher sensitivity or lower noise, is in demand. Conventionally, the improvement of the response characteristics is attempted by use of materials configuring layers, such as the free layer configuring the MR elements, and by optimization, such as film thickness of the layers, and the like. However, there is the problem that it is very difficult to further improve the response characteristics by these attempts.

SUMMARY

Reflecting on the above problem, the objective of the present embodiment is to produce a magnetic sensor and a magnetic encoder that have two types of magnetoresistive effect elements requiring response characteristics different from each other, and that can improve different response characteristics required for the magnetoresistive effect elements.

In order to solve the problem, the present embodiment produces a magnetic sensor, provided with at least a first magnetoresistive effect element and a second magnetoresistive effect element that can detect an external magnetic field, wherein the first magnetoresistive effect element and the second magnetoresistive effect element are a plurality of layers of a multilayer body including at least a free layer where its magnetization direction varies according to the external magnetic field; when at least the free layer of the first magnetoresistive effect element and at least the free layer of the second magnetoresistive effect element are viewed from the upper side in the lamination direction, both the free layers have shapes that are different from each other; the shape of at least the free layer of the first magnetoresistive effect element viewed from the upper side in the lamination direction of the first magnetoresistive effect element is a shape that can increase the slope of output of the first magnetoresistive effect element relative to the change of the external magnetic field; and the shape of at least the free layer of the second magnetoresistive effect element viewed from the upper side in the lamination direction of the second magnetoresistive effect element is a shape that can decrease the slope of output of the second magnetoresistive effect element relative to the change of the external magnetic field compared to the slope of the output of the first magnetoresistive effect element.

According to the embodiment, the different response characteristics required for first and second magnetoresistive effect elements can both be improved by setting the shape of the first magnetoresistive effect element requiring that the slope of output be great (an output change is exponential) and that of the second magnetoresistive effect element requiring that the slope of output be smaller than that (an output change is linear) to have the appropriate responsive characteristics.

In the embodiment above, the shape of at least the free layer of the first magnetoresistive effect element can be a polygon with M+N sides (M is an integer of 3 or greater, and N is an integer of 1 or greater); and the shape of at least the free layer of the second magnetoresistive effect element can be a polygon with M sides; it is preferable that the shape of at least the free layer of the first magnetoresistive effect element be a polygon with M+N sides (M is an even number of 4 or greater, and N is an integer of 1 or greater); and the shape of at least the free layer of the second magnetoresistive effect element is a polygon with M sides; and it is preferable that the shape of at least the free layer of the second magnetoresistive effect element be a shape having at least two facing sides parallel to one another.

Also, in the embodiment above, the shape of at least the free layer of the first magnetoresistive effect element can be nearly circular, and the shape of at least the free layer of the second magnetoresistive effect element can be nearly square-shaped.

In the embodiments above, a TMR element or a GMR element can be used as the first magnetoresistive effect element and the second magnetoresistive effect element; and in the embodiments) above, it is preferable that the first magnetoresistive effect element and the second magnetoresistive effect element be formed by laminating a magnetization pinned layer, a non-magnetic intermediate layer and the free layer in this order. In the embodiment above, it is preferable that the non-magnetic intermediate layer be MgOX(X=0.1 to 0.9). In the embodiments above, it is preferable that the non-magnetic intermediate layer be a multilayer body at least including a first non-magnetic intermediate layer and a second non-magnetic intermediate layer.

Further, the present embodiment produces a magnetic encoder, that has the magnetic sensor according to the above embodiments; and a scale part that has an absolute signal track where absolute magnetic signals are recorded and an incremental signal track where incremental magnetic signals are recorded, and that is movable relative to the magnetic sensor, wherein the magnetic sensor and the scale part are placed to face each other so that the first magnetoresistive effect element and the absolute signal track face each other and the second magnetoresistive effect element and the incremental signal track face each other.

According to the present embodiment, a magnetic sensor and a magnetic encoder can be produced that each include two types of magnetoresistive effect elements requiring mutually different response characteristics, and can both improve the different response characteristics required for each magnetoresistive effect element.

