my particles are typically made on Mica, I was wondering if mica or even glass can be used for such measurements.
also for SQUID and VSM could the sample be in liquid phase? if so how the sample is gotten prepared?
You can use both mica and glass for substrates if the magnetic signal of nanoparticles is strong enough. In any case you have to measure the signal of the substrate and next subtract it from the total magnetic signal.
Measurements of liquid phases are possible in SQUID and VSM but samples should be sealed in quartz tubes (the pressure in measuring chamber is low and can cause evaporation of a liquid). I recommend to immerse sealed tube in liquid nitrogen beforte the measurement because sometimes tubes breake in low temperatures.
Hi. Flat surfaces such as mica, sapphire, MgO or even glass are suitable for all of those techniques. As Bartlomiej pointed out, you should measure the substrates alone (i.e. without the particles) to characterize their magnetic behavior, which is normally diamagnetic unless many magnetic impurities are present (and in that case they may behave as paramagnetic materials).
Regarding MFM, if your particles are big enough to be ferromagnetic, you can obtain the magnetic structure: single domains or multidomains (in general, the latter case for bigger particles). However, if your particles are small. i.e. below a critical size that depends on their magnetic anisotropy, they may behave as superparamagnets and in that situation you only obtain an attractive contrast, since the magnetic moment of the particles would always be magnetized by the stray field from the MFM tip.
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