I measured hysteresis loop for LiCd ferrite, but hysteresis loop showed a strange behaviour: magnetization increased with applied field then when field increased magnetiztion started to decrease. what is this behaviour? why this happens?
Dear Mr. Aly,
at my opinion this is a problem of the physics. If we have a bulk softmagnetic ferrite
with great dimensions, so we have a "normaly" hysteresys loop. If we have a thin layer or a nano particle, then we have other physic foundamentals. We have surface magnetic effects and spinwave effects, so we can get other hysteresis behaviors like in a bulk ferrite.
All the best
F. Gräbner
you please mention the type of sample? Is it a thin film on some substrate?
I suspect that this is due to the pole saturation effect at high fields. What fields are you measuring up to?
As the field increases beyond a critical threshold, the permeability of measurement pole pieces decreases, which manifests as an apparent decrease in the magnetization of the measured specimen.
Generally, the effect is most noticeable at field > 1T, but for weak samples it can be seen at 0.9-1.0 T. The exact field where this occurs depends on the setup of the VSM (i.e., the gap between the pole pieces) and the behavior of the pole pieces.
Most VSM software has the functionality to correct for this, but you will probably need to calibrate the correction. If you regularly change the gap between the pole spaces you will need to regular check the pole saturation calibration. In theory, it depends on the exact gap between the pole pieces, but it often turns out to be relatively insensitive in practice, but you should always check your machine characteristics.
I hope this helps.
So you do not have a loop.Is it a straight line? In that case it could be paramagnetic?
I too am observing unusual loops with SrFeOx ferrites. The behavior is astonishing.
Please contact me for an explanation. [email protected]
Brian Ahern Acton MA 01720
This observation might be due to a mixture of diamagnetism and ferromagnetism. In fact, the diamagnetic causes the drop. I believe this happens at small magnetizations where the diamagnetic part of the mixture can have an effect on the magnetic part. If you subtract the diamagnetism, you will see a regular hysteresis loop. Sometimes the VSM measurement software has the capability of subtracting diamagnetism and paramagnetism.
Hi Muhammed,
Could you please attach a figure of your loop. This will really help us determine what is happening.
I have shown 2 examples loops in the attached PDF. The top row shows an example of diamagnetic effects. Here the sample is very small and surrounded by a lot of diamagnetic plastic and this causes the negative high field slopes (left side). Correction rectifies this (right hand side).
The bottom row show the effects of pole piece saturation. In the case it is only clear at very high fields (~1.8T) where the magnetization drops. Again, this can be corrected for (right hand side).
I too would like to see the loop. We are thinking ferromagnetic/antiferromagnetic transitions are important as well.
Please, cuold you attach the loops, make a description of the sample and the VSM instrument that are you using.
Cd is cadmium
The sample is a lithium cadmium ferrite , which is made of lithium, cadmium, iron and oxygen.
If the variation is linear it could mean that it is just paramagnetic at the T you measured.
Strontium ferrite has a most unusual loop when pulses rapidly. Any explanations would be helpful.
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