http://www.hindsinstruments.com/applications/polarization/magneto-optic-kerr-effect/?gclid=CODVqaas27MCFUV66wodUU0Aiw

Instead of the expensive PEM you can use a Faraday modulator, which consist of a 10 cm long glass rod within a coil. Using lock-in amplifying you will achieve a comparable signal-to-noise ratio. The advantage of the Faraday modulator is that you can measure absolute values of the Kerr angles, the disadvantage is that you have to perform two measurements for ellipticity and rotation (with and withour lambda quarter plate), while the PEM allow for simultaneous measurement of both properties using a two-channel lock-in amplifier. If it has to be even more cheap you can omitt the lock-in-amplifier. But then you have to pay with signal-to-noise ratio. In this case you detune polarizer and analyzer slightly and measure the transmitted light intensity as noise free as possible.

PEM usually provides a good sensitivity. However, instead of PEM one can use a Faraday cell (a long rod of glass with high Faraday rotation, placed inside a solenoid connected to the AC current source). The Faraday sell allows to modulate the polarization rotation angle. The cell can be hand made.

I have build a MOKE wirh the following parts: Laser (solid state laser greeen wavelenght), two polarizators, two lens(one to focus the beam into the sample and the other one to focus the outgoing beam to the detector (a photodiode only sensitive to the wavelenght of the laser.), a PEM.

The PEM is essential if you are measured materials with a low kerr rotation, for ferromagnetic metasl it is not neccesary. The magnets with a bipolar source to drive the mscans of the magnetic fields. If you need more information please read the next parper: http://onlinelibrary.wiley.com/doi/10.1002/adma.201javascript:101513/pdf

If you have further questions please do not hesitate to ask me again

Please refer to my papers on measurement of MOKE using PEM.

K.Sato: Measurement of Magneto-Optical Kerr Effect Using Piezo-Birefringent Modulator; Jpn. J. Appl. Phys. 20 [12] (1981) 2403-2409.[Citation 112 (May 4, 2010)]http://home.sato-gallery.com/research/JJAP_20_2403_1981.pdf

K.Sato, H.Hongu, H.Ikekame, Y.Tosaka, M.Watanabe, K.Takanashi and H.Fujimori: Magnetooptical Spectrometer for 1.2 - 5.9 eV Region and its Application to FePt/Pt Multilayers; Jpn. J. Appl. Phys. 32 Part 1 [2] (1993) 989-995

http://home.sato-gallery.com/research/JJAP_32_989_1993.pdf

Sato San's papers set the early benchmark for MOKE setups and the measurement principle is very well described in his papers. Certainly those are helpful. Also look up Prof. John Cerne and his work on MOKE. His 2003 RSI paper has discussions on various aspects of PEM based MOKE setup. What sort of setup you need really depends on what sensitivity range you are addressing, as Helena has indicated. MOKE involves both rotation and ellipticity measurements and without a PEM it is difficult to measure both simultaneously. But if you are looking to measure extremely small effect, in the range of micro degrees, you should probably look for homodyne polarimetric setup with differential detection and a ultra low noise pulsed or ac magnetic field. PEM will not be helpful. Sub millidegree to few degrees range can be addressed best using PEM and analyzer combination. PEM will also allow you to calibrate your setup for absolute polarization measurements. A rotating analyzer can also ideally achieve 10s of millidegree sensitivity (without PEM) but is difficult to measure ellipticity in the same experiment as in rotation. However, if you are looking for large rotation, cheapest solution is use of polarizer + analyzer combination. All these measurement will need 1 or more lock-in amplifier. You should look for a lock-in amp that can do 1f, 2f and 3f simultaneously up to 200kHz. Plus the method that Prof. Elmers has mentioned using Faraday modulator, which can be home built as well. Also if you have any EOM handy, open it, remove the front and back polarizers (most cases) and you can use it as polarization modulator (you will need to replace the RI fluid inside).

As for magnets you should again look at what you are really trying to address, polar / longitudinal / transverse MOKE and choose magnet pole pieces based on sample geometry and accessibility. We build most of our magnets and power supplies ourselves so I will not be able to help you with vendors, but check out gmw, oxfordmagnets etc. I have seen one other thread in RG discussing electromagnet vendors, look it up. Keep in mind, in most cases for MOKE measurements you will probably not need a very large magnetic field.

PEM setup is not essential if you chose a stabilized laser. Quartz polarizer (Glan-Thomson or Taylor) is needed to have a high distinction ratio. You may read some related papers, such as SMOKE or recently we have a new result for SMOFE (Faraday effect). We have successfully measured 1 nm magnetic films without any heating treatment. If you plan to setup the facility, welcome to discuss with us. C. W. Su, [email protected]

Quantum Design in India offers Nano MOKE from Durham Magneto-optics. See details in attached link http://www.durhammagnetooptics.com/products/nanomoke3/

PEM, 2 polarizers (Glan thompson) intensity stabilised laser such as He-Ne CW 2-5 mW, photo conductive or photovoltaic detector, lock-in-amplifier such as SRS845, optical stands for mounting the various components, 50 Or 75 mm dia pole piece electromagnet, programmable current source (for above small magnets, even keithley make 5A Sourcemeter is a perfect choice for small samples), and a lab view loaded PC witg GPIB card and two cables is all that what you need to set up a MOKE MH setup without any back ground of Optics. We are routinely able to record hysteresis loops on 2.5 nm thin magnetic films.

Hope this helps.

I see there are Green Laser Modules that have two additional wire leads for TTL signal to operate in modulation mode. Wouldn't that be a cheaper solution as opposed to PEM or Faraday modulator or chopper? (provided that you already have a lockin amplifier)

We can use both Green and Red Lasers. But Green Laser is preferable. Now a days most of the people are using this instrument to measure optical properties of magnetic materials. Lock in amplifier is important in this.