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Science Forum Index » Materials Forum » Magneto-optic Kerr effect
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| Bala Ramadurai |
 Posted: Thu Jul 31, 2003 2:10 pm |
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Hi everybody,
My setup consists of a 650nm LASER, chopper, polarizer, sample in magnetic
field, polarizer 2 and detector. the detector and chopper and connected to a
lock-in amplifier. I have not been able to get a hysteresis loop so far.
I have a few questions regarding this.
1. How much should the angle typically be between the polarizers ?
2. I have a digital reading output on the lock-in which can go upto 2
units. how much should this reading normally be ?
3. how much will the change in reading be for a Co thin film, say.
4. how much is the output in terms of just voltage from the lock-in ?
Thanks
Bala |
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| Nils Dalen |
| Posted: Fri Aug 01, 2003 6:18 pm |
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Guest
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Bala Ramadurai <nikimonikado@yahoo.com> wrote in message news:<bgbt2l$oot$2@news.asu.edu>...
Quote: Hi everybody,
My setup consists of a 650nm LASER, chopper, polarizer, sample in magnetic
field, polarizer 2 and detector. the detector and chopper and connected to a
lock-in amplifier. I have not been able to get a hysteresis loop so far.
I have a few questions regarding this.
1. How much should the angle typically be between the polarizers ?
I don't know exactly what your system is or what you are trying to do,
but:
when I made a very simple kerr looper (no chopper or lockin). I put
the 2 polarizers crossed (rotate for zero signal from the detector
before you apply a field). Then, any Kerr rotation will cause an
increase that should be detected.
Quote: 2. I have a digital reading output on the lock-in which can go upto 2
units. how much should this reading normally be ?
3. how much will the change in reading be for a Co thin film, say.
How thick is your Co film? If you are using a chopper/lockin setup, I
figure you are looking at very thin (monolayer?) films. Start with
something thick and check it first to be sure it has a signal.
E.g. Start with a thick film (>300A). Check the film first with some
other method (VSM, SQUID, BH-looper) to be sure it is good. Don't use
the chopper or the lockin, just look for raw signal from the detector
for now. Start with the polarizers crossed (zero output). Sweep the
magnetic field and see if there is any signal in your detector. A
thick Co film should give signal that you can see without a chopper.
Quote: 4. how much is the output in terms of just voltage from the lock-in ?
A lot of these other questions depend on specifics of your detector.
Look up what the Kerr rotation is for cobalt, and calculate how much
light will get through your crossed polarizers. From the sensitivity
of your detector, you should be able to calculate the signal.
One last question--you do have a filter on your detector, right? It
is only able to see the 650nm laser line and no ambient light? Also,
are you sure your magnetic field is operational?
Nils |
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