It all depends on the detector you're using. If it is a through the lens detector, a high magnetic field is placed around the sample. This can cause the nano particles to accelerate towards the detector.
It all depends on the detector you're using. If it is a through the lens detector, a high magnetic field is placed around the sample. This can cause the nano particles to accelerate towards the detector.
We routinely image magnetic fine powders. Sometimes the images are not sharp due to the effect of the magnetic field produced by the sample on the beam trajectory, resulting in inevitable distortions. Further, if the powder particles are sputtered by the beam they can accumulate at the detector, which will then need special cleaning
I would say, please try to use minimum amount of magnetic materials for analysis. As David mentioned that it depends on detector. These days, In-lens detector are routinely used that may cause some problems if you are not taking care while analysis. I have done several imaging on 5 nm to 30 nm sizes of magnetite, cobalt, Ni, nanoparticles, but never experienced any problem even in case of inlens detector. Similarly, I have done HR-TEM imaging (at 200 kV) on these nanoparticles where only few particles are randomly dispersed over the substrate.
In short, sample preparation is key to get nice image.
Thanks all for your answers it really helped. I just want to clarify what I understood to make sure that I didn't misunderstood.
So by applying the electron beam on the magnetic nanoparticles they magnetize and upon magnetization they will be sputtered and if the detector of the device is an in-lens detector the nanoparticles will be sputtered towards it resulting in its malfunction?
If right, can i just ask how will electrons magnetize the nanoparticles? since the electron beam is not an electromagnetic wave.
I think, the problem is merely the magnetic fields emerging from the electromagnetic lenses of the electron optics, certainly not the electrons themselves. I also know that this issue as apparently solved by the company Zeiss, who developed an electron optic which does not produce a magnetic field within the sample chamber and is hence particularly interesting for the examination of magnetic samples.
In order to avoid problems associated with sputtering the particles from the surface of the sample we had made measurements on small flakes of the sample rather than on finely powdered sample.
Dear Yasmine, the particles may be sputtered by the mechanical energy of the electron beam. The particles are already magnetized, and if the characteristic size of the particles is small enough (below the single-domain critical size) each particle behaves like a small magnet, and may get stuck at the surfaces of the nearby magnetic elements. I would think that the interaction of the electron beam with the lines of force produced by the magnetic particles may perturb the beam trajectory and influence the quality of the image negatively
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