Why can't scanning electron microscopy (SEM) detect magnetic powder samples with too many requirements for large samples?

1, the most important thing is that the sample should not touch the probe! 2. Before putting the sample, the sample must be fixed to avoid falling off. If the powder sample is not well adhered, it should be blown off to avoid blocking the passage of the electron gun. 3. The injection must be dry. 4. There are some things that are not considered as safety priorities, such as controlling temperature and humidity, not making too much vibration and noise, wearing gloves when taking and placing samples, and so on.