My magnetic result is so different from others' results. Does anyone know how to explain the plot? I am so confused. Furthermore, when it adds -8000 Gauss the curve turns to zero. Is this result normal? Please help me, thank you!
Could you please add more information like, what's i your sample? Is there a substrate? What is it made of?
The negative slope on the right of your curve could be a diamagnetic response from the substrate, for example. The signal from the substrate is usually subtracted from the curves before publication. So your curve could appear to be different from published results because of it.
@Nicholas
There was only di water and iron nano particle. The magnetic field was added from 10000 Gauss to -10000 Gauss. So I guess it was probably normal condition?
Thank you for your help!!!
So water is diamagnetic wich means it has a negative susceptibility. So that negative slope to the right probably comes from water. You can subtract it from your experimental data, just make a linear fitting in the points for positive fields, and subtract a straight line with the slope coefficient from you fitting. Remember to substract from ALL you experimental data and use ONLY the SLOPE coefficient from the fitting. Then you will have the signal from you sample.
Dear Annie,
- It would be interesting to know how exactly your particle was mounted on the sample holder. What kind of sample holder did you use? Was it a quartz paddle or did you use a container for powders? Did you mount just one particle or an agglomerate of particles? Is it possible that your sample was not attached firmly and was moving during the measurement?
- How many data points are in the field interval from -10000 to -8000 G? I have a suspicion that the instrument was not measuring anything in this interval, as the graph looks completely flat there. Can you repeat the measurement for the field, say, from -20000 to 20000 G (and back to -20000 G)? Also, it is worth taking an M(H) curve for a calibration sample (usually it is a nickel sphere often supplied with the instrument) to make sure that there is no offset in the system and the M(H) curve looks sensible.
Dear Annie Chen:
- It seems that the high field linear part from your data is the diamagnetic contribution from the water and/or the container/sample-holder used for mounting your sample. As pointed out by Nicholas Figueiredo, you should substract this linear part from all your raw data.
- If possible, follow the directions from Mikhail Kustov as a way to discard any instrumental artifact or mounting problem, and for collecting more reliable data. It is very important to verify that your magnetometer was calibrated and is measuring the true zero-field. You shluold also avoid any additional sample displacement and/or off-centering during VSM measurements.
- I think that you only are observing the upper half of the full hysteresis loop (the -H,+M; and the +H,+M quadrants). Also, it looks like nothing has been measured betwwen -8kG and -10kG. If you can collect data from a wider field intervall, probably you will be able to observe the full hysteresis loop.
- Finally, -after discarding any measurement error-, You've stated that your system contains exclusively iron nanoparticles in DI-water; so I would like to ask: If your iron nanoparticles are protected against oxidation?
If the answer is no, and you are still facing a hysteresis loop that is not centered at the origin, it is possible that your system is exhibiting Exchange-Bias. This phenomena may happen when the nanoparticle's surface is oxidized and produces a core/shell structure. In your system, you may have a ferromagnetic iron core coupled with an antiferromagnetic iron oxide shell, being this the cause of shift in your hysteresis data.
Article Microscopic origin of exchange bias in core/shell nanoparticles
Thank you for all the suggestions. The sample was made in di water and I believe the nano iron contains oxygen inside because the material did expose in the air.
The vsm plot was add from +10000 Gauss to -10000 Gauss. Also the plot did not subtract the di water plot.
Afterwards, we did do anther vsm analyze subtracted the di water plot, yet the result is still different from usual one.
I would like to show the plot but I am outside I will upload the plot later. Thanks again!!!
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