Electricity: measuring and testing – Magnetic – Magnetometers
Reexamination Certificate
2002-10-28
2004-03-16
Le, N. (Department: 2862)
Electricity: measuring and testing
Magnetic
Magnetometers
C324S260000
Reexamination Certificate
active
06707298
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a magnetic sensor comprising a magnetoresistive effect element and a coil for generating a magnetic field which is applied to the magnetoresistive effect element.
2. Description of the Related Art
Magnetic sensors have hitherto been known which employ as a magnetic field detection element a magnetoresistive effect element such as a giant magnetoresistive effect element (GMR element) or a magnetic tunnel effect element (TMR element). As shown in
FIG. 33
, such a magnetic sensor may comprise a coil
110
for applying a bias magnetic field to a magnetoresistive effect element
100
. In this case, the coil
110
is formed spirally, and the magnetoresistive effect element
100
is formed above the spiral of the coil
110
,and between the center of the spiral and the outermost circumferential part in a plan view. The bias magnetic field applied to the magnetoresistive effect element
100
is generated by electric current flowing through windings of the coil
110
positioned immediately below the magnetoresistive effect element
100
.
However, according to the above prior art, the coil
110
includes large part that does not contribute directly to the forming of the bias magnetic field, which results in the large occupancy area of the coil
110
in the sensor, posing a problem that the coil
110
will be an obstacle to the miniaturization of the magnetic sensor. Another problem is that because the overall length of the coil
110
is increased with its increased resistance, the power consumption for generating the bias magnetic field will increase, or that because the electric current that might be necessary with a limited power supply voltage can not be secured, it will be difficult to form a desired bias magnetic field.
SUMMARY OF THE INVENTION
The present invention was conceived in order to address the above problems. According to a first aspect of the present invention there is provided a magnetic sensor comprising a thin-film-like magnetoresistive effect element; and a coil formed in a plane parallel to a planar film surface of the magnetoresistive effect element, the coil generating magnetic fields applied to the magnetoresistive effect element; wherein the coil comprises a first conductor forming a spiral in a plan view, and a second conductor forming a spiral in a plan view; wherein the magnetoresistive effect element is disposed between a spiral center of the first conductor and a spiral center of the second conductor in a plan view; and wherein the first conductor and the second conductor are connected such that electric currents in substantially the same direction pass through a part of the first conductor at a portion overlapping the magnetoresistive effect element in a plan view and through a part of the second conductor at a portion overlapping the magnetoresistive effect element in a plan view. The above magnetoresistive effect element can include a giant magnetoresistive effect element, a magnetic tunnel affect element, etc.
Thus, the magnetoresistive effect element is disposed between the spiral center of the first conductor that is spiral In a plan view and the spiral center of the second conductor that is spiral in a plan view, and an electric current in substantially the same direction passes through a portion of the first conductor at a portion to overlap the magnetoresistive effect element in a plan view and a portion of the second conductor at a portion to overlap the magnetoresistive effect element in a plan view. As a result, since large part of the conductor forming the coil can be used for generating the magnetic field applied to the magnetoresistive effect element, the occupancy area of the coil in the sensor can be reduced.
In this case, preferably, the part of the first conductor at the portion overlapping the magnetoresistive effect element in a plan view and the part of the second conductor at the portion overlapping the magnetoresistive effect element in a plan view are formed rectilinearly parallel to each other.
Thus, since an electric current flows in parallel with each of the conductors passing immediately under the magnetoresistive effect element (at a portion to overlap the magnetoresistive effect element in a plan view), each magnetic field generated by the electric current flowing in each conductor does not offset each other. Therefore, the magnetic field applied to the magnetoresistive effect element can be generated efficiently (without wasting the electric power).
Preferably, widths of the first and second conductors at the portion overlapping the magnetoresistive effect element in a plan view are equal, the widths being different from widths of the first and second conductors at the remaining portions.
Thus, the resistance value of the entire coil can be reduced, while an electric current of the magnitude necessary for generating a magnetic field of a predetermined magnitude is being applied to each conductor passing immediately under the magnetoresistive effect element, thereby making it possible to lower the power consumption.
In such a magnetic sensor, the coil can be used as a coil for generating a magnetic field to confirm whether or not the magnetoresistive effect element functions normally. In the case where the magnetoresistive effect element is a magnetoresistive effect element (e.g., a giant magnetoresistive effect element) including a free layer and a pin layer, the coil can be used as a coil to generate a magnetic field for initializing the direction of magnetization of the free layer. Further, in the case where the magnetoresistive effect element is a magnetic tunnel effect element, the coil can be used as a coil to generate a bias magnetic field for the magnetic tunnel effect element to detect the magnetic field applied to the element.
According to a second aspect of the present invention there is provided a magnetic sensor comprising a substrate; a first magnetic detection portion (unit) formed on the substrate, the first magnetic detection portion indicating a physical quantity which increases (which becomes larger) as the magnitude of a magnetic field in a first direction in a first orientation increases, the first magnetic detection portion indicating the physical quantity which decreases (which becomes smaller) as the magnitude of a magnetic field in the opposite direction to the first direction in the first orientation increases; a second magnetic detection portion formed on the substrate, the second magnetic detection portion indicating a physical quantity which increases (which becomes larger) as the magnitude of a magnetic field in a second direction in a second orientation that crosses (e.g., at right angles) the first orientation increases, the second magnetic detection portion indicating the physical quantity which decreases (which becomes smaller) as the magnitude of a magnetic field in the opposite direction to the second direction in the second orientation increases; a first testing coil disposed in the vicinity of the first magnetic detection portion (e.g., burled under the first magnetic detection portion within the substrate), for generating a magnetic field whose magnitude and direction change in the first orientation depending on electric current flowing therethrough, the first testing coil applying the generated magnetic field to the first magnetic detection portion; a second testing coil disposed in the vicinity of the second magnetic detection portion or buried under the second magnetic detection portion within the substrate, for generating a magnetic field whose magnitude and direction change in the second orientation depending on electric current flowing therethrough, the second testing coil applying the generated magnetic field to the second magnetic detection portion; an electric current supply source; a connection conductor for connecting the first testing coil and the second testing coil in series to the electric current supply source: and a conduction control circuit interposed in a closed circuit which compr
Kaneko Makoto
Sato Hideki
Suzuki Toshihisa
Dickstein Shapiro Morin & Oshinsky LLP.
Yamaha Corporation
Zaveri Subhash
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