JPH09289344A - Magnetic sensor - Google Patents

Abstract

(57) Abstract: A magnetic sensor capable of measuring the polarity and magnitude of a magnetic field without a bias structure. By measuring a voltage generated in a magnetic thin film in a direction perpendicular to a current direction, the direction of a magnetic field and / or
Alternatively, measure the magnitude of the magnetic field.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a magnetic sensor.
More specifically, it relates to a magnetic sensor capable of measuring the polarity and magnitude of a magnetic field by utilizing the planar hole effect.

[0002]

MR heads are currently being developed for reading in order to achieve high density magnetic recording. this is,
This is a device that utilizes the anisotropic magnetoresistive effect, and is a phenomenon in which the voltage generated in the current direction changes with the magnitude of the magnetic field.

[0003]

However, when the anisotropic magnetoresistive effect is used, for example, the magnetic field is +10 O.
Since the same output (the same sign and absolute value) is obtained with e and −10 Oe, it is difficult to clarify the polarity of the magnetic field. Therefore, the current MR head solves this problem by applying a magnetic field bias.

However, this bias structure is generally complicated, and the yield of the devices is very bad at the time of mass production. An object of the present invention is to provide a magnetic sensor capable of high-density recording capable of determining the polarity of a magnetic field and simultaneously measuring the magnitude of the magnetic field without a bias structure.

[0005]

According to the present invention, the polarity of the magnetic field can be clarified by measuring the planar hole voltage generated in the direction perpendicular to the current direction. This voltage is a voltage generated perpendicular to the current direction. Therefore, the planar hole voltage can be measured by making the device have a four-terminal structure.

According to the present invention, by measuring the planar hole voltage, it is possible to determine the polarity of the magnetic field without a bias structure, and it is possible to stably mass-produce magnetic field read heads from a magnetic recording medium. . The polarity of the magnetic field can be determined by measuring the planar hole voltage, and the polarity of the magnetic field and the magnitude of the magnetic field can be measured by reading the voltage. Therefore, the measurement of the planar hole voltage can be used for determining the polarity and / or the measurement of the magnitude of the magnetic field, and may be combined with the MR element as required. Since the MR element has a larger output, M is required to measure the magnetic field.
R elements are preferred.

[0007]

EXAMPLE A theoretical comparison between the anisotropic magnetoresistive effect (AMR effect) and the planar hole effect will be considered. Both of them are phenomena peculiar to magnetic materials, and it is generally said that two types of carriers are present in the two-carrier mode.
l is understood. The electric field generated in the current direction and the direction perpendicular to the current direction when a current is passed in the longitudinal direction of the sample is calculated. When the electric conductivity and mobility of the two types of carriers are σ ₁ , σ ₂ , μ ₁ , and μ ₂ , the potential difference (V _amr , V _hall ) in the current direction and in the direction perpendicular thereto is (1), ( It becomes like the formula 2). The expression (1) is the AMR effect, and the expression (2) is the planar hole effect.

[0008]

[Equation 1]

In the formula, a: distance between electrodes J: current density (A / cm ² ) σ: electric conductivity μ: carrier mobility Δρ: resistance change amount w: pattern width Both effects are the movement of two carriers It can be seen that a difference in potential causes a potential difference.

The pattern produced is shown in FIG. Si (10
0) NiFe film on the substrate by the ion beam sputtering method,
Basic pressure 8 × 10 ^-8 Torr, processing pressure 8.5 × 10 ^-5 Torr
It was deposited at a film thickness of 110 nm at a deposition rate of 1.1 Å / sec. The current direction pattern 1 has a width w = 0.2 mm, a length 4 mm,
The voltage measurement patterns 2 and 3 have a pattern interval of 2 mm and a width of 0.
The length was 2 mm and the total length was 4 mm (the current direction pattern 1 was located at the center of the total length). The magnetic field was applied in the direction of H in the figure.

The anisotropic magnetoresistive effect (FIG. 2) is measured by measuring the voltage parallel to the current direction, and the planar hole effect (FIG. 3) is measured by measuring the voltage perpendicular to the current direction.
Was measured with the same sample. The magnetic field was applied perpendicular to the current. From FIG. 2, MR ratio: 1.8%, Δρ: 0.51 μΩ
cm was obtained. Using the formula (1), 1 / (σ ₁ +
σ ₂ ), Δρ are obtained from the experimental data, and the change in voltage is plotted against the rotation angle θ of the magnetization. It can be seen that the experimental results can be reproduced quantitatively.

Therefore, the results of the calculation of the planar hole voltage based on the parameters obtained from the experimental data of the anisotropic magnetoresistive effect (AMR) are also shown in Y of FIG. It is confirmed by comparing FIGS. 4 and 3 that this also agrees well with the experimental data. The output voltage is quantitatively almost equal. Therefore, it was confirmed that the magnetic field from the magnetic recording medium can be detected with zero bias and the direction (polarity) of the magnetic field can also be detected by using the planar hole effect.

It is understood that the planar hole effect (FIG. 4) confirmed as described above has a behavior in which the AMR effect is differentiated with respect to θ, and zero bias driving can be performed unlike the AMR effect. The planar hole effect is
It is expected that the output voltage will reverse from positive to negative at the zero magnetic field. At this time, the sensitivity of the AMR is zero (the differential with respect to the magnetization rotation angle is zero), whereas the sensitivity of the planar hole effect is maximum.

FIG. 5 shows a structural example of a magnetic head for carrying out the present invention. In the figure, 11 is a magnetic recording medium, which moves in the direction of arrow A. Reference numeral 12 is a magnetic head, which is a magnetic film 13.
Are formed in parallel with the magnetic recording medium 11 and in a direction B perpendicular to the moving direction A thereof. MR terminals 14 and 15 are provided at both ends of the magnetic film 13 in the B direction, and planar hole voltage terminals 16 and 17 are provided at both ends of the magnetic film 13 in the A direction with an insulator 18 interposed therebetween.

A current is passed between the MR terminals to measure the voltage (change) between the planar hole voltage terminals 16 and 17. If necessary, the resistance (change) between the MR terminals is measured.

[0016]

The present invention using the planar hole effect is
It is a major feature that it can be driven with zero bias and has a simple element structure while having the same output and sensitivity as a conventional magnetic head (MR head) using the anisotropic magnetoresistive effect. Therefore, a significant yield improvement is expected for mass production of heads.

[Brief description of drawings]

FIG. 1 shows a film forming pattern of an example.

FIG. 2 shows the anisotropic magnetoresistance of the NiFe film of the example.

FIG. 3 shows the planar hole effect of the NiFe film of the example.

FIG. 4 shows calculation results of anisotropic magnetoresistive effect and planar hole effect.

FIG. 5 shows a structure of a magnetic head of an example.

[Explanation of symbols]

 1 ... Current direction pattern 2, 3 ... Voltage measurement pattern 11 ... Magnetic recording medium 12 ... Magnetic head 13 ... Magnetic film 14, 15 ... MR terminal 16, 17 ... Planar hole voltage terminal 18 ... Insulator A ... Medium movement Direction B: Direction perpendicular to medium movement

Claims (6)

[Claims] 1. A magnetic sensor characterized by detecting only a magnitude of a magnetic field by measuring a voltage generated in a magnetic thin film in a direction perpendicular to a current direction. 2. A magnetic sensor, which detects only a direction (polarity) of a magnetic field by measuring a voltage generated in a magnetic thin film in a direction perpendicular to a current direction. 3. A magnetic sensor, wherein the magnitude and direction (polarity) of a magnetic field are simultaneously detected by measuring a voltage generated in a magnetic thin film in a direction perpendicular to a current direction. 4. A magnetic sensor, which detects the magnitude and direction of a magnetic field by measuring both a voltage generated in a current direction and a voltage generated perpendicularly to the magnetic thin film. 5. The magnetic sensor according to claim 1, 2, 3 or 4, wherein the magnetic substance is Fe, Ni, Co or an alloy thereof. 6. A magnetic sensor using the magnetic sensor of claim 1, 2, 3, 4 or 5 for a head for reading magnetic recording.