Vibrating sample magnetometer VSM principle and applications

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Vibrating sample magnetometer (VSM) principle
and applications
Content 1. Introduction 2. Principle of VSM 3.
Configuration 4. Measuring and analyzing
methods 5. Remarks
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1. Introduction

• Magnetic measurement is a powerful method to
  characterize properties of materials.
• Among numbers of magnetic measurement equipment,
  Vibrating sample magneto-meter (VSM) is known as
  a very effective way to determine magnetization.
• VSM offers different measuring modes. By
  analyzing the results, many useful information of
  materials can be extracted.

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VSM sample is vibrating with a standardized
frequency ( ) during the measurement. H
does not depend on t but M depends on t AC
measurements always improve signal to noise
ratio. By this method, the signal is directly
proportional to magnetization.
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3. Configuration

• VSM DMS model 800
• Maximum magnetic field 1.4 Tesla.
• Field step 1Oe
• Sensitivity 1x10-5 emu (mAm2)
• Vector coil configuration enables magnetic moment
  can be determined in the direction parallel and
  perpendicular to the field (Mx My)
• Angular controller -80o - 440o, step 0.5o
• Temperature controller 77K-700K
• Measuring process is controlled by an accompanied
  software. Different measurements can be set in a
  sequence.
• Samples
• Bulks
• Powders
• Thin films

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4. Measuring and analyzing methods
VSM is used to measure the magnetic properties of
materials as a function of magnetic
field, temprature,and time

• 4.1. Hysteresis loop measurement Different
  modes
• Full loop Half loop 5-10 Segments
• Major loop
• Saturation magnetization Ms
• Coercivity Hc, Remanence Mr Squareness S
• Switching field distribution SFD
• (BH)max
• Minor loop
• Virgin curve measurement

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• 4.2 Remanence measurements
• Isothermal remanence magnetization (IRM)
  measures remanence, start from demagnetized state
• DC demagnetization (DCD) measures remanence,
  start from demagnetized state
• ?M curve By comparing IRM and DCD curves,
  magnetic interaction of materials can be
  predicted (based on Stoner-Wohlfarth mode).

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4.3 Angular dependent measurement Hysteresis
loops as well as remanence curves can be measured
at different angles From the angular dependence
of some parameters (Hc, Mr), magnetization
switching mechanism can be determined coherent
or incoherent rotation etc. 4.4 Time dependence
measurement Magnetization relaxation can be
studied by this method. 4.5 Torque
measurement Torque signal can be obtained from
magnetization perpendicular to the field
direction L(?) ?0MyH
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Angular dependence of Hc
Thermo-magnetization curve
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• 4.6 Thermo-magnetic measurement
• Ms(T) determines magnetic phases, Curie points,
  ratio of different phases.
• Mr(T) determines compensation point
• Other transition points can be detected Spin
  reorientation temperature
• Field cooled (FC) and zero field cooled (ZFC)
  determine blocking temperature in fine particles
  system.

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5. Remarks

• As VSM is a very sensitive magnetometer, careful
  corrections are needed to obtain faithful
  results
• In thin films, which have low magnetic moment,
  the diamagnetic effect must be subtracted from
  the whole signal.
• In some cases, demagnetization field has to be
  taken into account, especially in case of thin
  film with magnetization out of the film plane.
• Magnetic history of materials have to be
  considered to analyze results AC demagnetized,
  DC demagnetized.
• Disadvantages
• Not very high field
• Temperature dependence measurements take long
  time.