JPH0296676A - Magnetic field sensor - Google Patents

Abstract

PURPOSE:To enable miniaturization of a Faraday rotation element 1 by forming the element of an alloy of a CdTe-MnTe-ZnTe system. CONSTITUTION:A magnetic field sensor uses a Faraday effect material made up of an alloy of a CdTe-MnTe-ZnTe system as a Faraday rotation element. Since this Faraday effect material has a large Verdet constant, sufficient sensitivity can be obtained without setting the length of a crystal substance constituting the Faraday rotation element to be large, and the magnetic field sensor thus obtained can be used for measurement of magnetic field even in a narrow place.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to, for example, a magnetic field sensor for detecting current flowing in a power transmission line or distribution line or a magnetic field, or a magnetic field sensor for flaw detection or a magnetic field sensor for power measurement. The present invention relates to a magnetic field sensor using Faraday effect materials such as.

[Prior art] When a magnetic field is applied externally to a magneto-optical material with good tip permeability, such as lead glass, Zn5e crystal, or BSO crystal, and light is transmitted in the same direction as the magnetic field, light passes through the magneto-optic material due to the Faraday effect. It is known that the plane of polarization of light rotates during this process. The rotation angle θ (min) of the polarization plane is given by the following formula.

θ-VHQ.

Here, ■ is the Verdet constant (min10e-cm), H
represents the strength of the magnetic field (Oe), and i represents the length of the Faraday rotation element (cm).

This magnetic optical rotation phenomenon can be used to measure magnetic fields. FIG. 8 shows the basic configuration of a magnetic field sensor using the Faraday effect. In FIG. 8, incident light passes through an optical fiber 1 and a rod lens 2, passes through a rectangular parallelepiped-shaped polarizer 3, becomes a linearly polarized wave, and then enters a similarly rectangular parallelepiped-shaped Faraday rotator 4, where it enters. Under the influence of the magnetic field 5, the plane of polarization is rotated by an angle θ and exits from the Faraday rotating water T4. The rotation angle θ of the plane of polarization at this time
is replaced by the intensity of light by a rectangular parallelepiped analyzer 6 placed on the output side of the Faraday rotator 4. Then, this light passes through the rod lens 7 and the end fiber 8 and becomes an emitted light 10, and IIl+ can be determined by detecting the intensity of this emitted light with a photodiode.

In the magnetic field sensor shown in FIG. 8, the Faraday rotation element 4 is made of lead glass, Zn5e crystal, BSO crystal (Bi+2
Optical crystals such as 5i02o) are used, and their sensitivity is expressed by the Verdet constant V, which at a wavelength of 850 nm has the following value.

Lead glass 0.01 minloe-cmBSO
Crystal 0.10 m1n10e-crnZnSe crystal 0.15 m1n10e fist cm [Problem to be solved by the invention] However, all of the above-mentioned conventional optical crystals had a small Verdet constant value, and therefore had low sensitivity. In order to obtain practical sensitivity, it is necessary to obtain a constant rotation angle θ, but as is clear from the above 2〇−VHη, when the Verdet constant value is low, the length store of the Faraday rotator It was necessary to set the length to, for example, about 5 to 30 mm.

For this reason, in the case of a conventional magnetic field sensor using Faraday effect material, the sensor becomes large and a problem arises in that it becomes difficult to measure the magnetic field in a narrow place.

The primary objective of the present invention is to provide a magnetic field sensor that can be miniaturized by using a Faraday effect material that exhibits a large Verdet constant value.

[Means for Solving the Problems and Their Effects] In order to solve the above-mentioned problems, the present inventors have conducted various studies on Faraday effect materials that have a larger Verdet constant H than conventional ones, and as a result, CdMrr T Z to e-based alloy
It was discovered that a Faraday effect material with a large Verdet constant could be obtained by alloying nTe, and this invention was made.

That is, the magnetic field sensor of the present invention is made of CdTe-MnT.
It is characterized by using a Faraday effect material made of an e-ZnTe alloy as a Faraday rotation element.

Further, it is preferable that the Faraday effect material used in the magnetic field sensor of the present invention has a composition within the following composition range. That is, as shown in the attached FIG. 1, Cd0.
, Mn0.5 Zno, 2 Te (CdTe30%,
MnTe50%, ZnTe20%), CdO, Mr+0
．． 5 zno, + Te (CdTe40%, MnTe
50%, ZnTe 10%), Cd.

I S Mn, ), 4 Zn(,,65Te (CdT
e55%.

MnTe40%, ZnTe3°u), Cdo, 71
Mno, 2 zno, 05're (CdTe75
%, MnTe 20 z'01 Z n Te 5
%), Cdo, 8 Mn+), I Zno, I T
e (CdTe80%, MnTe10%.

ZnTe 10! '6), Cdo, I Mn,), I
Zno, 2Te (CdTe70%, MnTe
1O! '6. It is preferable that the composition be within the range (including the boundary line) surrounded by ZnTe (20% ZnTe).

The Faraday effect material used in the magnetic field sensor of this invention has a large Verdet constant, and in particular, those with a composition within the range shown in Figure 1 have a Verdet constant of 2.00 [1].
The Verdet constant is (-j) of 10e-Cm or more. Therefore, conventional Faraday effect materials such as lead glass and B
Compared to SO crystals, Zn5e crystals, etc., it has a large Verdet constant of 10 to several tens of times. Therefore, in the magnetic field sensor of the present invention, the length a of the Faraday rotation element can be reduced to 1/10 to 1/10 of the conventional length. Therefore, the magnetic field sensor of the present invention can be miniaturized, and the magnetic field can be determined in a narrow place.

[Example] A crystal having a composition indicated by a circle in the ternary phase diagram of FIG. 2 was produced by the Bridgman method. C which is a high purity raw material 1″1
dTe, MnTe, and ZnTe were mixed in a graphite boat so as to have predetermined composition ratios, and the mixture was placed in a thick-walled quartz reaction tube and sealed under vacuum. This quartz reaction tube was placed in a horizontal electric furnace, and after heating and melting the raw materials, approximately 121
．． It was held for 17 hours.

Thereafter, the quartz reaction tube was moved at a slow speed to a low temperature section to cause crystallization from one end. The resulting crystal has a width of 20
ro m, length 200 mm, depth 10 mm, and was polycrystalline. A wafer with a thickness of 2 mm: t f, 1 is taken out from the center in the length direction of the crystal, and both sides are 11
The sample was polished to a mirror finish and had a thickness of 1 mm. As a result of 11'r, the structure of the obtained crystal was a single phase of zincblende crystal. The Verdet constant was measured for each sample at room temperature. 71p+constant wavelength is 660.730,780
, 850 and 1300 nm. Figure 3 shows 660
It is a ternary system phase diagram showing the Verdet constant of an example at a ΔPI constant wavelength of nm.

The E1 constant results for crystals with each composition ratio are
It is shown on the upper right of the point indicating the p1 stoichiometry. The unit is min
For a sample that is 10 e-cm and does not transmit light,
・Indicated.

Similarly, FIGS. 4, 5, 6, and 7 show Δpj constant wavelengths of 730 nm and 780 nm, respectively.
, Jp at 850 nm and l 300 nm
The results are shown below. 7111 shown in Figures 3 to 7
As is clear from the +constant result, the value of the Verdet constant is /Ip
+ constant varies with wavelength, but is highly dependent on the amounts of Mn, Zn, Te and Cd.

The shaded area shown in Figure 1 corresponds to the 11 area shown in Figures 3 to 7.
-1 constant Verdet constant is 2. The composition range shows an unprecedentedly large value of 0 min 10 e-cm or more.

Note that this composition range also includes a portion corresponding to the boundary line.

CdTe-MnTe-ZnT obtained as above
The magnetic field sensor of the present invention can be obtained by forming a Faraday rotation element from an e-based alloy, for example, as shown in FIG. 8, with a thickness of 1M.

Since the Faraday effect material f1 used in the magnetic field sensor of the present invention has a high Verdet constant H, sufficient sensitivity can be obtained without setting the length of the crystal body that constitutes the Faraday rotation element long. A magnetic field sensor capable of measuring a magnetic field even in a narrow place can be obtained. If a conventionally used Zn5e crystal or BSO crystal is used in a Faraday rotation element, for example, a length of 5 to 30 mm is required, but in this invention, the length of the crystal of the Faraday rotation element is It can be shortened to approximately 0.06 mm to 2.3 mm, and the magnetic field sensor can be miniaturized.

[Brief explanation of the drawing]

FIG. 1 shows a 2.0 m
FIG. 411 is a ternary system diagram showing an H1 component range showing a Verdet constant of i n10e-cm or more. FIG. 2 is a ternary system (1) diagram showing the composition measured in an example of the present invention. FIG. 3 is a ternary system phase diagram showing the Verdet constant of the example at the A1+ constant wavelength of 660 nm. Figure 4 shows 7
FIG. 3 is a ternary system phase diagram showing the Verdet constant of an example at a 14p1 constant wavelength of 30 n III. FIG. 5 is a ternary system phase diagram showing the Verdet constant of the example at the measurement wavelength of 780 n port 1. Figure 6 shows 850
It is a ternary system phase diagram showing the Verdet constant of an example at an API constant wavelength of +i m. Figure 7 shows Δ of 1300 nm.
FIG. 3 is a ternary system phase diagram showing the Verdet constant of the example at III constant wavelength. FIG. 8 is a conceptual diagram of 11 of the magnetic field sensor. In the figure, 1 is an optical fiber, 2 is a rod lens, 3 is a 1-photon, 4 is a Faraday rotation element, 5 is a magnetic field, 6 is an analyzer, 7 is a rod lens, 8 is an optical fiber, 9 is an incident light, 10 indicates the emitted light.

Claims (2)

[Claims] (1) In a magnetic field sensor that detects a magnetic field based on the rotation angle of the polarization plane of light passing through a Faraday rotator, the Faraday rotator is made of CdTe-MnTe-ZnT.
A magnetic field sensor characterized by being formed from an e-based alloy. (2) As shown in the attached FIG. 1, the CdTe-MnTe-ZnTe alloy is Cd_0_. _3Mn_0_
．． _5Zn_0_. _2Te (CdTe30%, MnT
e50%, ZnTe20%), Cd_0_. _4Mn_
0__. _5Zn_0_. _1Te (CdTe40%, M
nTe50%, ZnTe10%), Cd_0_. ＿５＿
5Mn_0_. _4Zn_0_. _0_5Te(CdT
e55%, MnTe40%, ZnTe5%), Cd_0
＿． _7_5Mn_0_. _2Zn_0_. ＿0＿5T
e (CdTe75%, MnTe20%, ZnTe5%)
, Cd_0_. _8Mn_0_. _1Zn_0_. ＿１
Te (CdTe80%, MnTe10%, ZnTe10
%), Cd_0_. _7Mn_0_. _1Zn_0_.
_2Te (CdTe70%, MnTe10%, ZnTe
The magnetic field sensor according to claim 1, wherein the magnetic field sensor has a composition within a range (including the boundary line) surrounded by (20%).