My doubt is regarding M-H measurement in MgB2 bulk superconducting samples.
I send my samples for M-H measurement in squid.
I got M-H data (magnetic moment vs magnetic field at fixed temperature), the maximum magnetic moment i got is 4 on both sides on hystersis loop.
that magnetic moment ranges from 0 to 4. Next time i take measurement on same sample from same place. I got magnetic moment which is ranges from 0 to 0.4 only.
so what is the mistake on measurement.why magnetic moment came very less value (in between 0 and 1 only)
whether some multiple of 10 is missing or some mistake happen by technitian during measurement. I need to know the error
Dear Himanshu,
did you measure the identical sample again, or another sample which should be equal to the first one?
If it's the identical sample, one simple possibility is a misalignment. This can easily happen when you mount the sample not exactly in the right position and thus have to interpret the signals in the right way - which may go wrong.
If it's not the identical sample but one which should be equal - well, this may happen. How do you prepare your samples? I remember some MBE produced thin film samples which surprised me since they behaved completely different from nominally identically produced ones.
Best,
Andrea
Next try after my first answer vanished:
Dear Himanshu,
firstly, are both samples identical (one and the same), or have they just been made in the same way?
In the first case, the sample may have been mounted at the wrong position (or better: the wrong position may have been assumed to be the sample middle) in the new measurement.
In the second case: This may happen. I remember some samples with quite unexpected results, behaving completely different from nominally identical ones.
Can you tell more about your sample(s)?
Best,
Andrea
Dear Dr Andrea Ehrmann
Thanks alot for focused on my problem. Here i have measured the same sample two times not the different samples. First i measure got quite good magnetic moment. After 10 days I measure I got very less magnetic moment on the same samples. Thing is that we are sending samples to other places. we dont know how they put the samples. My samples are bulk Mgb2 superconducting samples with dimension 3mm×3mm×2mm (length-breath-thickness).
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Dear Himanshu,
thanks for the information about your samples. Firstly, the relatively small dimensions may allow for adjusting errors (which can happen quite easily). Additionally, there may be some tilting - can you be absolutely sure that they were mounted both times in exactly the same orientation, i.e. not rotated by 90° or slightly tilted due to the gluing process?
Secondly, at which temperature did you measure? To my knowledge, pure MgB2 has a phase change between 19 and 20 K, so in this temperature area the temperature may be crucial.
Thirdly, as you mentioned yourself, you don't know the completely history of the sample. I don't know whether it can oxidize or perform some "self-doping" when left in air. However, I would simply measure the sample again and try to check all possible "geometrical" problems in detail before thinking about such physical reasons for your measurement differences.
Best regards,
Andrea
Dear Dr Andrea Ehrmann
I dont know how they measure. In which direction they put the sample. W e have measure our sample for M-H at fixed temperature at 10 K. Our sample is not sensitive it will not oxidized in air easily also. Yes i will try for next measurement. thanks alot.
With regards
Himanshu
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