JPH01218079A - Hall element and magnetic head - Google Patents

Abstract

PURPOSE:To fulfil two functions; electromagnetic conversion and waveform shaping simultaneously by using one Hall element, by causing two kinds of substances having different Fermi levels to be formed into a two-layer structure, thereby forming a potential gradient or barrier between the two layers. CONSTITUTION:A two-layer structure consisting of layers 10 and 12 having low and high Fermi levels is formed. If a current I flows in the layer 10 of low Fermi level, electrons move to the reverse direction. When a magnetic field B is impressed, the electrons are put aside by Lorentz's force. However, when the strength of the magnetic field B is less than the prescribed value, a potential V gradient or barrier obtained by the foregoing two-layer structure prevents electrons from moving from layer 10 to layer 12 and no electromotive force takes place. When its strength of the magnetic field B becomes more than the prescribed value, the electrons move from layer 10 to layer 12 and are stored in an electrode 20. Thus, electric polarization is formed between electrodes 18 and 20 and then, Hall electromotive force EH takes place.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a structure of a Hall element having nonlinear characteristics and a magnetic head using the same.

[Prior Art] A Hall element is a typical magnetic sensor and is used for non-contact detection of variables using a magnetic field as a medium.

FIG. 8 shows a conventional Hall element structure. When a current I is applied to the element 100 and the element 100 is placed in a magnetic field B, charged particles (electrons or holes) in the element 100 are subjected to Lorentz force in a direction perpendicular to both the current I and the magnetic field B, and are forced into one side of the element 100. Pushed to the side. This is a type of electric polarization, and the current
An electromotive force (Hall electromotive force) is generated in a direction perpendicular to the magnetic field B.

This Hall electromotive force EH is expressed by the following formula.

EH=KIBcosθ・・・・・・・・・(1
) Here, K is a proportionality constant (Hall coefficient), and θ is the angle between the normal to the element surface and the magnetic field B.

According to the above equation (1), the relationship between the magnetic field B and the Hall electromotive force EH has a linear characteristic as shown in Figure 9. For example, as shown in Figure 10 (a), for the magnetic field B changing sinusoidally, As shown in 10th (b), a Hall electromotive force EH that changes sinusoidally is obtained.

The material of the element 100 is an electrically uniform substance, S
i, InSb, GaAs, etc. are often used.

[Problem H to be Solved by the Invention] As described above, the conventional Hall element is a magnetic field-voltage conversion element (magnetic sensor) having linear characteristics as shown in FIG. Such an element is convenient for faithfully detecting the magnetic field as it is.

However, there may also be a Hall element having nonlinear characteristics as shown in FIG. 6, and this nonlinear characteristic may be convenient in some cases. For example, if a magnetic field that changes sinusoidally as shown in Figure 7 (a) is detected using a Hall element with such nonlinear characteristics, that single element can detect a rectangular shape as shown in Figure 7 (0). Wave signals can be generated. When using a conventional Hall element, there is no need for a waveform shaping circuit such as a comparator that is provided at the subsequent stage. A magnetic head is an example of an application of a Hall element having such nonlinear characteristics.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a novel Hall element structure having nonlinear characteristics and a magnetic head using the same.

[Means for Solving the Problems] In order to achieve the above object, the Hall element of the present invention has a two-layer structure in which layers of two types of substances with different Fermi levels are stacked, and for supplying current. A pair of electrodes were connected to the surface of the layer with the lower Fermi level, and a pair of electrodes for detecting the Hall electromotive force were connected to the opposing surfaces of both layers.

The two types of substances are preferably metals and semiconductors, such as nickel silicide and chromium silicide.

Furthermore, the magnetic head of the present invention has a Hall element having the above structure.

[Effect] When two materials A and B with different Fermi levels (different work functions) as shown in Figure 3 (A) and (0) are joined, the potential inside the materials becomes as shown in Figure 3 (C). It will look like the one shown. Furthermore, when an n-type semiconductor and a metal are bonded, for example, as shown in FIG. 4(a), the potential within the material becomes as shown in FIG. 4(c).

Therefore, the potential within the two-layer material in the Hall element of the present invention becomes as shown in FIG. 3 (c) or FIG. 4 (c).

As shown in FIG. 5, the lower Fermi unit layer 10
When a current I flows in the direction of the arrow, electrons as charged particles move in the opposite direction (downward in the figure). On the other hand, when magnetic field B is applied in the direction of the arrow, electrons are pulled sideways by the Lorentz force.

However, because there is a gradient or barrier in the potential V from the layer 10 with a lower Fermi level to the layer 12 with a higher Fermi level, electrons cannot move to the layer 12 while the strength of the magnetic field B is small. Therefore, no electric polarization is formed, and no Hall electromotive force El is generated. Then, when the strength of the magnetic field B increases and exceeds a certain value, some of the electrons either overcome the potential or are removed from the layer by tunneling. Moving on to 12, it is also pulled to the side by the Lorentz force and accumulates in the electrode 20 on one side, thereby forming electric polarization between the electrodes 18 and 20 and generating a Hall electromotive force Ell.

Due to this effect, the relationship between the magnetic field B and the Hall electromotive force EH has a nonlinear characteristic as shown in FIG. By controlling the potential gradient or barrier by changing the thickness of the layer 12 with a higher Fermi level below a certain value, it is possible to change the threshold value BO of the magnetic field.

In a magnetic head equipped with a Hall element having such nonlinear magnetic field-Hall electromotive force characteristics, when converting a magnetic signal into an electric signal and performing waveform shaping, a single Hall element performs two functions: magnetoelectric conversion and waveform shaping. Since the functions are performed simultaneously, no special (dedicated) waveform shaping circuit is required.

[Example] FIG. 1 is a sectional view showing the structure of a Hall element according to an example of the present invention, and FIG. 2 is a plan view thereof.

In these figures, 10 is a layer of nickel silicide;
12 is a layer of chromium silicide. These layers overlap to form a two-layer structure.

A pair of electrodes 14 and 18 for supplying current are connected to both ends of the upper surface of the nickel silicide layer 10, respectively. Terminals 14a and 18a of these electrodes are electrically connected to an output terminal of a constant current power supply circuit (not shown). In the intermediate part i of the element, a pair of electrodes 18 and 20 for extracting the Hall electromotive force are connected to the opposing surfaces of both layers, that is, the upper surface of the nickel silicide layer 10 and the lower surface of the chromium silicide layer 12. be done. Terminals 18a, 20a of these electrodes are electrically connected to, for example, an input terminal of a buffer circuit or an amplifier circuit.

22 is a glass substrate.

To create such a Hall element structure, the electrode 14.1
6, 18.20 by depositing aluminum,
Both silicide layers 10 and 12 may be formed as thin films by vapor deposition. At this time, it is preferable to prevent impure contaminants from entering the interface between both layers 10 and 12.

The direction of the magnetic field B applied to this Hall element is perpendicular to the direction in which the current flows (the longitudinal direction of both layers 10 and 12) and the direction in which the Hall electromotive force is taken out (the thickness direction of both layers 10 and 12). becomes.

In the Hall element with such a structure, the potential within the nickel silicide layer 10 and the chromium silicide layer 14 is as follows:
The potential is roughly similar to the potential in Figure 3 (c). Further, the same effect as described above with respect to FIG. 5 is performed, and a nonlinear magnetic field-Hall electromotive force characteristic as shown in FIG. 6 is obtained. Therefore, when the magnetic field B changes sinusoidally as shown in FIG. 7(a), an output signal Ell as shown in FIG. 7(b) is obtained at the terminals 18a+20a.

Therefore, if this Hall element is mounted on a magnetic head and used to reproduce digital signals, a single Hall element can simultaneously perform two functions: magnetoelectric conversion and waveform shaping, so a special (dedicated) waveform shaping circuit is required. No longer needed.

[Effects of the Invention] As described above, the Hall element of the present invention has a two-layer structure of two types of materials with different Fermi levels, creating a potential gradient or barrier between the two layers, and increasing the magnetic field strength to a certain value. By generating the Hall electromotive force from the time when the magnetic field exceeds the threshold, a nonlinear magnetic field-Hall electromotive force characteristic can be obtained.

Further, the magnetic head of the present invention has a Hall element having nonlinear magnetic field-Hall electromotive force characteristics, so that a single Hall element simultaneously performs the function of converting a magnetic signal into an electric signal and the function of shaping a waveform. Therefore, there is an advantage that there is no need to use a special waveform shaping circuit.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the structure of a Hall element according to an embodiment of the present invention, FIG. 2 is a plan view of the Hall element according to the embodiment, and FIG. FIG. 4 is a diagram showing the internal potential when an n-type semiconductor with different Fermi levels and a metal are joined together. FIG. 5 is a diagram schematically showing the operation of the present invention. FIG. 6 is a diagram showing nonlinear characteristics obtained by the present invention; FIG. 7 is a signal waveform diagram showing an application example of the present invention; FIG. 8 is a conventional Hall element. FIG. 9 is a schematic perspective view showing the structure; FIG. 9 is a diagram showing linear characteristics obtained by the Hall element shown in FIG. 8; FIG. 10 is a signal waveform diagram for explaining the function of the Hall element shown in FIG. 8. . In the drawings, 10... Nickel silicide, 12... Chromium silicide, 14.16... Current supply electrode, 14a, 16a... Electrode terminal, 18.20... Hall origin. Power extraction electrode, 18a+
20a... Electrode terminal, 22... Glass substrate.

Claims (3)

[Claims] (1) It has a two-layer structure in which layers of two types of substances with different Fermi levels are stacked, and a pair of electrodes for supplying current are connected to the surface of the layer with a lower Fermi level, respectively,
A Hall element characterized in that a pair of electrodes for extracting Hall electromotive force are respectively connected to mutually opposing surfaces of both layers. (2) The Hall element according to claim 1, wherein the two types of substances are a metal and a semiconductor. (3) The Hall element (4) according to claim 1, wherein the two types of substances are nickel silicide and chromium silicide.
A magnetic head comprising the Hall element according to claim 1.