A few thoughts...
1. Could it be a heating effect?
Is the effect the same on all corners of the sample?
Hi Les,
Thanks for chiming in.
I don't see how it could be a heating effect... that would *reduce* the magnetism (if we could get beyond the Curie temperature, which we can't in a thermally conductive material).
The effect (degree of beam deflection) is different in every part of the sample, but it is a complex sample of cm sized blocks of various pure metals including Ni, Fe and Cr...), so that would be expected?
2. Could it be a charging effect?
I recall that someone saying 40% of the 2nd'y electron yield comes from the polepiece via BSE.
So, these BSE could be BSE'd back onto the sample somewhere else to possibly charge.
I would imagine that this would be cylic though.
No, it is not. The degree and direction of beam deflection goes with the sample rotation- yes, we tested that on Monday!
Also the SE image shows zero charging.
3. Lastly, the sample should not be magnetised by the beam unless the beam creates a magnetic field.
M=BILsin(theta). 'I' you have, the rest is anyones guess.
Yes, that is the question.
4. If the beam is magnetising the sample, it should be 'I' dependant.
But then again, so should heating and charging.
We have not tried different beam currents, but it is a good suggestion... we'd have to demag the sample each test and carefully time the degree of beam deflection. It is very strange...
Now really pressing hard...
5. Local heating may allow the magnetic domain boundaries to migrate. This may cause localised magnetic variations but this is just a guess.
Again I don't think so. See above, #1