I'm afraid that magnet particles will be able to deposition on microscope details due they magnet properties. How can I prepare this particles on support so that they do not fly into the microscope?
Dear sosnin, first you need to disperse the MNPs into a solvent which could be DI water, methanol or ethanol either 100% or diluted. Later, take for bath-ultrasonication for 10-20 min. Then, take a single drop of the ultrasonicated suspension, and put it on the copper grid until vaporizes and then you can view with no harm using SEM.
You do not need copper grid if you are planning to to apply conductive coating to your particles. Any smooth surface (plastic, glass) will work. When your solvent dried out, Van der Waals forces will keep particles in place.
If you want to avoid coating, then you need to use copper grid with carbon film on it - they are used for TEM specimens.