A+Magnetization+Measuring+Instrument—Vibrating+Sample+Magnetometer

A Magnetization Measuring Instrument—Vibrating Sample

Magnetometer

ZHAO Ruijuan1,2 AN Panlong1

1 Department of Physics, School of Science, North university of China, Taiyuan, 030051, 2 Department of Physics, School of Science, Xi’an Jiaotong University, xi’an, 710049

Phone: +8613571945487

etc. Abstract: A measurement mechanism is introduced

in this thesis, which is usually used in the Key words: Vibrating Sample Magnetometer;

production 、research and development of the working principle; constitution of the system;

Applied for instance magnetic materials and can accurately measure the

magnetic characterization curve of this magnetic I. Introduction material, it is the most popular magnetization

measuring instruments, Vibrating Sample In the research and production of the Magnetometer（VSM）. It uses an open-circuit magnetism material, the magnetization intensity or

magnetizing force of the materials is already needed technique in which the magnetization measurement

to know, and the curve of magnetic characters is is based on the measurement of flux changes when a

sample moves through the detection coils. The also needed to be precisely measured. The test

technique of Vibrating Sample Magnetometer was simplest measurement of the magnetic flux change

put forward by S. Foner in 50’s, which synthesized is the extraction method, in which a sample initially

the advantage of two methods of magnetic induction at the center of the detection coil in the presence of

and magnetometer in magnetic measurement. In a field is quickly moved to a point far away from the

recent years, its sensitivity was largely raised and coil. The change in flux, which is proportional to

its usage scope was expanded, with the the magnetic moment of the sample, is calculated by

development of the modern electronics technique integrating the electromagnetic force (emf) induced

particularly because of the development of in the detection coil. It emphasis on the operating、

phase-lock and amplification technique. It not only principle、characteristic、construction and function

of the high degree of accuracy of the Vibrating carries on the measurement of the automatic

powder、Sample Magnetometer, and also proceed the precision to the magnetic character of disk、

analysis of data sampling、data handling and soft and hard thin films、permanent magnetism and calculation, which uses computer as interface. single crystal or amorphous materials, such as, Finally, 7404 model of Vibrating Sample magnetic curve、magnetic hysteresis loop、coercive

force、magnetic torque、permeability、remnant Magnetometer is taken as an example, which is used

to characterize the magnetic properties of magnetism and Curie temperature, etc, but also (FePt/C)10 multilayer films. The magnetic measure the magnetic character of magneto-optical

recording thin film materials, which was very thin hysteresis loop、the isothermal remanence (IRM)、

and its saturation intensity was small and can not be the DC demagnetization (DCD) and the moment M

vs. time (M -t plot) are measured by VSM. These measured by normal Vibrating Sample

Magnetometer. parameters are most often used to characterize the

magnetic properties 、investigate the intergranular

exchanging and the thermal stability of materials,

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II. Brief recommendation of Vibrating Sample Magnetometer

1. Measure principle

V≈?Nμ0S

dHz3NS?A?ω?M?a

exp(iωt) =5

dt4πr

Therefore, as long as the position(a, b), area(S), the

full circle number(N) and the vibrating frequency of the sample（ω）、oscillation （A ） were all certain, then the respond electric voltage V will a linearity direct proportion to the sample magnetic torque M, namely V=G?M, we can carry on a test to make sure the proportion factor G in the sample of the

Mshave already known.

2. The system constitution

The basic constitution of Vibrating Sample

Magnetometer was shown in fig. 2:

Fig.1 Measure principle

Such as fig.1 shows, unmeasured sample can be looked as a magnetic dipole, which was supposed to be located at origin o, and supposed its magnetization intensity was M, its direction was X, it could vibrate by the angular frequency of ω, its oscillation was A. If we put a test coil in A（a,b,0）, it will create a magnetomotive Φ(z) in coil because of the magnetic dipole, its magnitude was:

Φ(z)=

M?a222

, r=a+b+z 3

4πμ0?r

As the magnetic dipole was in brief vibrating,

z=A?exp(iωt)

Φ(t)=Φ(0)+A?exp(iωt)=Φ(0)+

dΦ(z)dz

Fig. 2 The system constitution

3?A?M?a?z

?exp(iωt)5

4πμ0?r

The magnetic field in coil was:

Hz(t)=?gradΦ(t)=[

3A?M?a

?exp(iωt)] 5

4πμ0?r

The coil sectional area of the point A was S, its full circle number was N, the output electric voltage in the coil then is:

3. System characteristics

1) The non- integral calculus type-collect

synchronously, have no zero shifts;

2) The principle is simple, the usage is

convenient, applying fields is wide;

3) Time that spot measurement need is short; 4) The sensitivity is high. 4. Functions

By making use of the function of sampling and controlling interface of the computer and choosing

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to use some accessories, we can carry on an automatic sampling to the sample, and handle and revise the data that we have collected, so that we can acquire the magnetize curve and various parameter of the material. The system can draw the curve immediately by the exterior equipments and the X-Y scanner linking in the meantime, or print the curve of the parameter with the printer, can also save disk to carry on the contrast analysis. We can also by loading various accessories combination to carry on other measurement in addition.

III. Apply for instance

7407 type vibrating sample magnetometer can be used to come to token various magnetic recording medium, GMR, CMR, exchange to be

Fig. 3 The magnetic hysteresis loop of （FePt/C）10 partial to press, spinning valve and magneto-optical

material, including of a piece of material, powder, thin film, single crystal and the liquid material, and be extensively applied for the testing of the antimagnetic, paramagnetic, ferromagnetic, ferrimagnetic, antiferromagnetic and anisotropic property materials.

The following is mainly introduce the application of 7407 type Vibrating Sample Magnetometer in the aspect of the token to magnetic recording medium, and show Vibrating Sample Magnetometer is very important in the research and production. The following figure 3, figure 4, figure 5, figure 6 is that

Fig. 4 The DC demagnetization of （FePt/C）10 we measured the magnetic property curves of

magnetic recording multilayer thin film（FePt/C）10 by

The interaction of crystal grains within 7407 type Vibrating Sample Magnetometer:

Fig.3 was a magnetic hysteresis loop of magnetism material would have decisive influence to

the macroscopic magnetism property of the material. （FePt/C）10, we can directly get three parameters of

Fig. 4 and fig.5 were two curves that measured by the multilayer thin film （FePt/C）10 from the fig. 3,

7407 type of VSM, which were the DC which were saturation magnetization Ms、residual

demagnetization (DCD) and the isothermal remanence magnetization Mr and coercive force Hc, can also get

（FePt/C）10. The relations of these two kinds some else parameters, which were rectangle (IRM) of

ratio(Mr/ Ms) of this curve, rectangle ratio S* of of curves can be used to describe the interaction of coercive force and the switch field distribute(SFD) etc. inner crystal grains of magnetic body.

These were very important to magnetic recording

materials, and high density magnetic recording

medium was requested that Hc was high and SFD was

small.

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Fig. 5 The isothermal remanence (IRM) of （FePt/C）10

Fig. 6 The moment M vs. time (M -t plot) of （FePt/C）10Fig.6 was the relation curve of magnetization intensity M vs. time (M -t plot) ,which are measured directly by VSM under the magnetic field -Hc. Correspondingly, the slope of the curve of M(t)- Ln(t) was the magnetic coefficient of viscosity S of that material. By S, we could calculated magnetic activating bulk Va of that material, got its thermally stable factor, and made sure the thermal stability of that material finally. REFERENCES [1] Dodrill B C. Magnetic media measurements with a VSM Lake Shore Cryotronics,Inc. [2] S. Foner. Rev. Sci. instrum., 1959,30(7): 548 [3] S. Foner. Rev. Sci. instrum., 1968,39(2): 171 [4] The development of multi-function intelligence vibrating sample magnetometer, 《The electricity measures and the appearance》, 1994, 9：12 [5] The application of Vibrating Sample Magnetometer in magnetic recording medium, 《the information recording material》, 2005, 6（2）

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A Magnetization Measuring Instrument—Vibrating Sample

Magnetometer

作者：

作者单位：ZHAO Ruijuan ， AN PanlongZHAO Ruijuan (Department of Physics, School of Science, North university of China, Taiyuan,

030051;Department of Physics, School of Science, Xi'an Jiaotong University, xi'an, 710049)，

AN Panlong(Department of Physics, School of Science, North university of China, Taiyuan,

030051)

2007 引用本文格式：ZHAO Ruijuan .AN Panlong A Magnetization Measuring Instrument—Vibrating Sample Magnetometer[会议论文]