What applied field is required for M-T (FC & ZFC) and can I do M-H measurement from zero to 5 T and how much should the increment of applied field be when I collect the data?
Are there any precuations I need to take to know the density of the film? If yes, how do I start?
Required applied field for M-T is depends upon the moments of the sample. You can try with 100-200 Oe magnetic field (for SQUID MPMS) and the see the sample centering is good or not. If the centering is not good then increase the applied field. Once sample centering os done then you can do M-T and M-H. Superconducting samples are diamagnetic and above the transition temperature they are generally paramagnetic. Also your sample is thin film. Therefore magnetic moment of your sample may be verry verry less and hence it will be verry difficult to measure. I'll recommend you to try with SQUID magnetometer.
Usually, for superconductors in modes FC&ZFC you have to apply so small field as possible, in order to see clearly difference of resulting magnetic moments between FC and ZFC and also to see transition temperature Tc (difference between s/c and normal states). From other hand, the values of magnetic moments have to be larger than those allowed by sensitivity of your experiment. The sensitivity is limited by sensitivity of device but also by subject (small amount of s/c film and relatively big amount of surrouding material - substrate, holder...).
M-H measurements at T=Tm which less but close enough to Tc could help you to find appropriate field H. It would be near minimum on the dependence M(H). I hope, that you'll find such minimum at H=Hm much earlier than you'll reach 5 T. So apply increment dH small enough (100, 50 or 10 Oe - depending on Hc of s/c and on difference Tc-Tm and look on the results - you can stop experiment and change dH or even Tm, if you see they are not appropriate. Such Hm will be appropriate for all T < Tm. Of course, M(H) needs preliminary cooling from r.t (T > Tc) to Tm at H=0.
@Kousik Bagani
I have access to PPMS, which has VSM with sensitivity of 10E-6 emu, if I do my measurement at T< Tc is there any hope for me to use this instrument for the measurement?
You can try with PPMS-VSM. But SQUID is the best instrument because sensitivity of SQUID is ~10E-8 emu......
Yes, SQUID is better but you can try to do it with PPMS-VSM, because the main problem could come from relatively big contribution of Si substrate. It is difficult to answer your question without knowing of film material (Tc, Hc) and thickness but for the worse case:
1st of all you have to do good centering of the sample: and be sure that you have a signal from your sample but not from other things. Check the signal at T> expected Tc and at T < Tc at any H which gives you good signal.
Try to measure bare substrate without film in order to estimate its contribution or to subtract its background latter. Do ZFC M(T) at Hm1 (let's say 100 Oe ) and M(H) at T close to expected Tc, up to H about 1.5 of expected Hc2.
For film+substrate (in the same orientation as substrate - for bigger signal at low H better to put its plane perpendicular to field). At H=0 cool the sample from r.t. to lowest possible T1 (ZFC), apply field Hm1 and run M(T) with step dT about 1/10 of expected (Tc-T1). Do 20 steps dT. Because of different contributions, all M(T) values could be even positive. Check signals. If there is superconductivity at Hm1, you have to see a stair on M(T). Do you see jump of M(T) (may be not very large) at T around expected Tc?
If, 'yes": find Tm< Tc but close as possible to Tc where the M ( Tm) confidentially less than M(T>Tc). Then do ZFC to Tm. Run M(H) from H=0 with step dH about 1/5 Hm1. Do you see M(H) so that it could be described as s/c characteristic with superimposed substrate's signal? Find approximately Hc's and after Hm where M(Hm) much less than M ( at H which is close but larger than Hc2 ). Run ZFC and FC at Hm. with small step around Tc.
If "no": you can repeat above procedures at Hm2 < Hm1 or look for other instrument or sample.
@ Gregory Leitus,
Thank you so much for the light that you have given to me in the above discussion, let me do some experiments and get back to you once again thanks a lot.
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