A kind of automatic biasing giant magnetic impedance sensor probe and preparation method thereof
Technical field
The invention belongs to informational function device technology field, relate to a kind of automatic biasing giant magnetic impedance sensor probe and preparation method thereof.
Background technology
Since nineteen ninety-four, the research of giant magnetoresistance effect is because it has great application prospect at Magnetic Sensor and area information storage, and various countries scientific worker's extensive concern extremely.Early stage research mainly concentrates on magnetic field and the frequency characteristic of studying various components and the impedance of material shape (silk, band and film) under different process conditions from theoretical and two aspects of experiment.The research of this respect has obtained important progress.In order to make giant magnetoresistance effect can better be applied to reality, current research emphasis is impedance rate of change and the sensitivity that how to improve giant magnetic impedance sensor.
Although compare with thread or strip material, membraneous material is more easily realized the microminiaturization of giant magnetic impedance sensor by photoetching etc. and integrated circuit processing technique, but because significant giant magnetoresistance effect is more easily observed in thread or banded magnetic material, so current commercial giant magnetic impedance sensor is all to be made by thread or strip material.But the reason due to magnetic material self-characteristic, the giant magnetoresistance effect that conventional magnetic material is embodied in the situation that not adding any disposal has nonlinear characteristic, and magnetoimpedance variation presents symmetry near null field, make the giant magnetic impedance sensor made insensitive to the variation in magnetic field at null field annex, sensitivity is low.
In order to improve this latent defect, academia and industry member adopt near the asymmetric giant magnetoresistance effect of null field can increase substantially the linearity and the high sensitivity of sensor.1), bias coil method asymmetric giant magnetoresistance effect thread or strip material can adopt following methods to realize:: by prepare coil on sensor, in coil, pass to electric current and produce bias magnetic field, if two giant magnetic impedance probes of setovering are in opposite direction connected with difference form, can realize near the linearity output of null field; But the method that adopts additional coils to produce bias-field not only will increase preparation difficulty and the expense of sensor unit, what is more important is to power up the power consumption that the raw bias-field of miscarriage can enlarge markedly probe, and this is that sensor does not wish to see when application.2), permanent magnet bias method: with mode 1) similar, adopt permanent magnet to replace bias coil, although this does not increase the power consumption of sensor, but can increase the volume of sensor, be unfavorable for the miniaturization of sensor.3), annealing method: amorphous strip material is not used and processed higher than the annealing temperature of crystallization temperature under magnetic field, can form surface crystallization layer, this surface crystallization layer (Hard Magnetic) produces the amorphous layer with inner (soft magnetism) exchange-coupling interaction and produces automatic biasing magnetic field, thereby make giant magnetoresistance effect be asymmetry [C.G.Kim, K.J.Jang, H.C.Kim, et al., J.Appl.Phys.85,1999,5447]].Because this asymmetric property is because exchange-coupling interaction forms, so power consumption is with respect to method 1) greatly reduce, volume is with respect to method 2) also greatly reduce, but because this Hard Magnetic/soft magnetism exchange coupling field forms by annealing, amorphous magnetic material is exposed in air easily oxidized, can make preparation sensor probe passing in time of job stability and reduce, the hard magnetic layer thickness limited (approximately 100 nanometer) that this annealing way of what is more important produces, make Hard Magnetic/soft magnetism exchange coupling field little, its null field linear work district less (being less than ± 2Oe), sensitivity is not enough.
Summary of the invention
The invention provides a kind of automatic biasing giant magnetic impedance sensor probe and preparation method thereof, described automatic biasing giant magnetic impedance sensor probe produces the principle in automatic biasing magnetic field based on the exchange coupling of Hard Magnetic/soft magnetism, can obtain the more linear work district of wide region, and significantly improve sensitivity, and have volume little, easy of integration, without the feature of extra power consumption; Its preparation method is simple, be conducive to suitability for industrialized production.
Technical solution of the present invention is:
A kind of automatic biasing giant magnetic impedance sensor probe, as shown in Figure 1, 2, comprise the banded magnetic material 2 of amorphous and the metal pair electrode 3 that is positioned at the banded magnetic material of amorphous 2 surperficial two ends, the banded magnetic material of amorphous 2 two sides between described metal pair electrode 3 deposit respectively one deck vectolite film 1; Upper and lower two-layer vectolite film 1 has along the consistent Hard Magnetic phase behaviour of banded magnetic material 2 length directions of amorphous.
A preparation method for automatic biasing giant magnetic impedance sensor probe, comprises the following steps:
Step 1: prepare the banded magnetic material of amorphous.Amorphous magnetic thin-band material is cut into the unit material of formed objects, is designated as the banded magnetic material 2 of amorphous, then the banded magnetic material 2 of amorphous is made to cleaning.Concrete cleaning process can be: first with conventional weak acid, weak caustic solution, clean the banded magnetic material 2 of amorphous, then with rinsed with deionized water, dry nitrogen, dry up stand-by.
Step 2: deposit cobalt ferrite film.Adopt rf magnetron sputtering thin film preparation process, the banded magnetic material 2 two sides deposit cobalt ferrite films 1 of amorphous after cleaning.
Step 3: photoetching.Adopt photoetching process, etch away two end portions vectolite film 1, on the banded magnetic material of amorphous 2 surfaces, reserve the deposition position of metal pair electrode 3.
Step 4: magnetize.Utilize magnet charger to processings of magnetizing of the vectolite film 1 of the banded magnetic material 2 two sides depositions of amorphous, upper and lower two-layer vectolite film 1 is presented along the consistent Hard Magnetic phase behaviour of amorphous band shape magnetic material 2 length directions.
Step 5: metal electrode preparation.The deposition position deposit metallic material of the metal pair electrode 3 reserving on the banded magnetic material of amorphous 2 surfaces is as metal pair electrode 3.Metal pair electrode can, in the banded magnetic material 2 one side preparations of amorphous, also can be prepared on the banded magnetic material of amorphous 2 two sides.
Through above step, can obtain automatic biasing giant magnetic impedance sensor probe of the present invention.
The present invention is coated with vectolite film (hard magnetic material) by magnetically controlled sputter method on the banded magnetic material of amorphous, then to the ferrite film processing of magnetizing, vectolite film is presented along the consistent Hard Magnetic phase behaviour of the banded magnetic material length direction of amorphous, vectolite film (Hard Magnetic phase) forms the effect of exchange Elastic Coupling with the banded magnetic material of amorphous (soft magnetism phase) like this, soft magnetism is carried out to automatic biasing mutually, make the banded giant magneto-resistance sensor probe of amorphous present asymmetric giant magnetoresistance effect.This make automatic biasing giant magnetic impedance sensor probe provided by the invention have volume little, easy of integration, without the feature of extra power consumption.
In addition; because rf magnetron sputtering thin film preparation process is prepared vectolite film hard magnetic material, than existing annealing process, Hard Magnetic is carried out in the banded magnetic material of amorphous surface; rf magnetron sputtering thin film preparation process is more easily controlled; the homogeneity of product obtaining is better; and rf magnetron sputtering is prepared vectolite film can obtain layer of oxide layer on surface; thereby internal layer amorphous magnetic material is played a protective role, the job stability of giant magnetic impedance sensor probe is improved.
Have again, in the present invention, can change by changing the thickness of vectolite film the size of self-bias field, thereby make to adopt giant magnetic impedance sensor probe of the present invention can adapt to the size that different demands is adjusted bias-field, to obtain more the linear work district of the sensor probe of wide region and the sensitivity of Geng Gao, and once the amorphous magnetic material that the giant magnetic impedance sensor probe that adopts annealing in process is selected is determined, its bias-field just immobilizes, and can not adapt to the diversity demand in actual use procedure.
Accompanying drawing explanation
Fig. 1 is automatic biasing giant magnetic impedance sensor probe planar structure schematic diagram provided by the invention.
Fig. 2 is the cross-sectional view of automatic biasing giant magnetic impedance sensor probe provided by the invention.
Fig. 3 is preparation technology's schematic flow sheet of automatic biasing giant magnetic impedance sensor probe provided by the invention.
Reference numeral: 1 is vectolite film, 2 is the banded magnetic material of amorphous, 3 is metal pair electrode.
Embodiment
Embodiment one
Adopt following process to prepare automatic biasing giant magnetic impedance sensor probe:
(1). selecting trade names is the Co of Metglass
82.17fe
4.45ni
1.63si
8.6b
3.15amorphous magnetic strip, its thickness is 30 microns, width 2mm, standby (being designated as: the banded magnetic material 2 of amorphous) of amorphous thin ribbon of reducing a segment length 30mm from strip.
(2). the banded magnetic material 2 of amorphous is carried out to following cleaning: with alkaline solution (ammoniacal liquor: hydrogen peroxide: deionized water=1:2:5) clean ultrasonic 15 minutes, with deionized water ultrasonic 5 minutes, with acid solution (hydrochloric acid: deionized water=1:8) ultrasonic cleaning is 15 minutes, with deionized water ultrasonic 5 minutes, with dry nitrogen, dry up.
(3). adopt rf magnetron sputtering thin film preparation process, the banded magnetic material 2 two sides deposit cobalt ferrite films 1 of amorphous after cleaning.Target adopts CoFe
2o
4, concrete rf magnetron sputtering technique is: back end vacuum 2 * 10
-6mbar, argon gas operating air pressure 1 * 10
-3mbar, oxygen operating air pressure 2 * 10
-4mbar, sputtering power 100W; Vectolite film 1 thickness is 2 microns.
(4). adopt photoetching process, etch away two end portions vectolite film 1, on the banded magnetic material of amorphous 2 surfaces, reserve the deposition position of metal pair electrode 3.
(5). utilize magnet charger to processings of magnetizing of the vectolite film 1 of the banded magnetic material 2 two sides depositions of amorphous, upper and lower two-layer vectolite film 1 is presented along the consistent Hard Magnetic phase behaviour of amorphous band shape magnetic material 2 length directions.Specifically magnetizing by magnetic field intensity is 5000 Gausses, magnetizes 10 minutes time.
(6). the deposition position deposit metallic material of the metal pair electrode 3 reserving on the banded magnetic material of amorphous 2 surfaces, as metal pair electrode 3, completes the preparation of automatic biasing giant magnetic impedance sensor probe.
The automatic biasing giant magnetic impedance sensor probe of preparing through said method, its linear work district is-5~+ 5Oe after tested, sensitivity is 476%/Oe.And only the performance of the automatic biasing giant magnetic impedance sensor probe by the same size of annealing under 300 degrees Celsius, 5000 gauss magnetic fields is: linear work district-1.5~+ 1.5Oe, sensitivity is 135%/Oe.As can be seen here, adopt preparation method of the present invention compared with annealing method, make the linear work district scope of amorphous thin ribbon improve 3 times, sensitivity improves nearly more than 2 times.
Embodiment two
Similar with embodiment one, just change amorphous magnetic thin-band material into (Co
94fe
6)
7si
10b
15amorphous magnetic strip (thickness is 25 microns, 2 millimeters of width, 15 millimeters of length), 1 micron of vectolite thickness.Its linear work district is-3.6~+ 3.6Oe after tested, and sensitivity is 325%/Oe.And only the performance of the amorphous thin ribbon giant magnetic impedance sensor probe by the same size of annealing under 300 degrees Celsius, 5000 gauss magnetic fields is: linear work district-1.5~+ 1.5Oe, sensitivity is 115%/Oe.As can be seen here, adopt preparation method of the present invention compared with annealing method, make the linear work district of amorphous thin ribbon improve 1 times, sensitivity improves nearly 3 times.
It should be noted that: the present invention is prepared in automatic biasing giant magnetic impedance sensor probe process 1, the thickness of vectolite film 1 can be controlled between 200 nanometers to 2 micron; 2, the target of preparing vectolite film is not limited to CoFe
2o
4, the atomic ratio in target between Co, Fe, O can regulate according to prior art; 3, concrete rf magnetron sputtering technique can be in following range: back end vacuum <5 * 10
-6mbar, argon gas operating air pressure 9 * 10
-4~9 * 10
-3mbar, oxygen argon is than 0.1~0.25, radio-frequency sputtering power 50-200W; 4, magnetize while processing magnetic field intensity and the time of magnetizing also without being defined in scope described in above-mentioned embodiment, as long as magnetize to process, can make upper and lower two-layer vectolite film 1 present along the consistent Hard Magnetic phase behaviour of banded magnetic material 2 length directions of amorphous.