If you have a saturated hysteresis loop, to remove diamagnetic contribución trom the substrate you simply substrate the slope obtained by linear fitting of the raw data at high field, where sample FM signal should be saturated= constant.

Dear colleague

You need to measure the sample holder without the sample. Then measure the sample with a sample holder. Thereafter, signal of the sample holder to subtract the signal sample with a sample holder. 

In my opinion this is the best way.

I agree with Dr. Koshkid'ko, however if your curve shows a sharp increase a very low temperatures (caracteristic of paramagnetic) you can fit this part of the curve with a Langevin function. The diamagnetic contribution must be very low in comparison with the ferromagnetic magnetization. See paper attached.

Dear Prof. Gallardo and Dr. Yu,

Thank you very much for your comments.

I can see only diamagnetic contribution at low temperature. As Dr. Yu suggested that measure the sample holder separately and subtract the contribution. But I think contribution from sample holder is very small however mm thick substrate gives large diamagnetic contribution. how to subtract this diamagnetic contribution from raw data?

If you have a saturated hysteresis loop, to remove diamagnetic contribución trom the substrate you simply substrate the slope obtained by linear fitting of the raw data at high field, where sample FM signal should be saturated= constant.

You can measure independently sample+substrate+sample holder, substrate+sample holder, sample holder. If you find substrate+sample holder is diamagnetic (linear), you can do linear fitting and obtain slope m and background offset c. Then use these m and c to subtract diamagnetic contribution in your  sample+substrate+sample holder data

Dear Shalu Pathak,

You may also take into account the material that you use to mount your sample onto the sample holder. Some of the tapes/glues sometimes used for this purpose are diamagnetic. This contribution into your overall signal can be negligible but it is worth checking (for example, several layers of PTFE tape generate quite a noticeable diamagnetic signal in a magnetic field).