I gave this presentation during my iii semester M.Sc program.This is about experiment technique to measure magnetization.Here we discuss induction method magnetometry.

1. Induction methods
magnetometry7%

2.  Frequently used unit of magnetic dipole moment in magnetism: emu/g
g
 Magnetization M is defined as magnetic moment/ volume
 Classification of magnetic behavior of material done on the basis of
bulk magnetic susceptibility×.
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3. WHAT IS MAGNETOMETER
A magnetometer is an instrument that measures magnetism—
either magnetization of magnetic material like a ferromagnet, or
the direction, strength, or the relative change of a magnetic field at
a particular location.
COMPASS.
In recent days, the magnetometers are used as compasses in tablet computers and mobile
phones.
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4. DISTINCTION
MAGNETOMETER-
GAUSSMETER IS RATHER
ARBITRARY AND NOT
COMMONLY USED
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5. Total field magnetometers or scalar magnetometers measure
the magnitude of the vector magnetic field.
Vector magnetometers measure the vector components of
the magnetic field.
Humans do not seem to have the ability to
sense either direction or the intensity of
magnetic field.
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6. SENSITIVITY RANGE OF THE
PROBE SHOULD COVER
WHOLE RANGE OF FIELDS
IN WHICH MAGNETIC
CONFIGURATION
SIGNIFICANTLY CHANGES
METHOD MOST RELEVANT
IN SPINTRONIC
MEASUREMENTS: AC AND
DC HALL PROBES
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7.  Stationary magnetometers
 Portable or mobile magnetometers:
.
 Survey magnetometers
 May be stationary as in INTERMAGNET network.
 May be mobile magnetometers scan a geographic region.
Laboratory magnetometers
 Typically Stationary.
 Unlike survey magnetometers , sample to be placed inside the magnetometer.
 The temperature, magnetic field etc. the sample can be controlled.
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8. This method depends on the Faraday's law of electromagnetic induction.
The electro motive force (e.m.f) induced in a circuit is equal to the rate of change of flux linking the
circuit.
Φ:magnetic flux passing through the coil
N :the number of turns in coil
Principle
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9. 60%

10. PICK UP COIL
• Analog
• A/C
Frequency(Hz)
Amplitude(Volts)
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11. 1.The sample should be an ellipsoid of revolution or be in the
form of thin film
2.the sample can vibrate along any direction
3.In principle it is enough to have one sensing coil
i. The second coil increases sensitivity.
ii. Reduces the noise due to external field.
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12. The sample moving to the right induces some voltage in
the right pick-up coil.
The voltage induced in the left coil has an opposite sign.
The coils are connected in reverse- so both
voltages add-sensitivity increases
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13. 1.The electromotive force generated in the pick-up coils is proportional to the
magnetization of the sample.
2.It depends too on the orientation of the magnetic moment relative to the coils.
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 Magnetization, linked to the magnetic field as:

14. the voltage depends on the
rate of change of induction B
 Depending on position of the coils the integral of the induction through the surface
bounded by the coils changes.
Digital
Voltmeter
Digital Integrator: Directly
gives change in flux.
Digital voltmeter Gives
rate of change of flux-but
Numerical Integration is
needed.

15. In measurement one usually
uses
static pick-up coils while the
sample
(and its magnetic field)
vibrates
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PRECAUTION
 Measure flux, not field. ⇒Calibration of geometry very important ; it
limits accuracy.
 Induction sensors can be sensitive both to magnetic field and electric field. An
electrostatic shielding should surround the sensor .

16. ADVANTAGES
 Even if new technologies have excellent performances ,Induction sensors (also known
as search coils) still the best way to achieve AC magnetic field measurements.
 Despite the disadvantage of their size , indispensable in numerous fields due to sensitivity
and robustness.
 Low costs and independent of temperature variations are two other advantages of the air
coil induction sensor.
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