I am getting average coercivity in the range of 0.099-0.144 kOe and M - H curves obtained from VSM for the applied field upto 1.5 Tesla and 2 Tesla are almost S shape. Please provide some good references also.
Savita Pannu
From an experimental point of view, superparamagnetism is characterized by two features: there is no hysteresis in the curve of the dependence of magnetization on the field σ(H) (the dependence of σ on H at a given temperature is unambiguous) and σ is a universal function of H/T.
It is important to note that superparamagnetism can be destroyed by cooling. This follows from the fact that the characteristic time of particle angular momentum fluctuations changes exponentially with temperature, and the magnetization quickly reaches a stable state as the temperature decreases. The temperature at which this occurs is called the blocking temperature. It depends linearly on the particle volume and
anisotropy values.
The blocking temperature is obtained using the ZFC and FC curves.
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A procedure to recognize the superparamagnetic behavior of the particles is by ZFC-FC curves at low magnetic field, as 100 Oe. ZFC (zero field cool, where sample is cooled without field and then is aplied increasing temperature between 5 and 300K por example). This curve measures M (magnetizacion) by temperature. Then, when ZFC curve has a maximum point denominated blocked temperature, and then when temperature is increased the magnetizacion decreases is identified a superparamagnetic. This together with the M(H) curve at room temperature is a rect line.
If the Squareness ratio of M-H Loop is equal to or less than 0.5 then you may say your sample is superparamagnetic which is highly sensitive in the presence of an external magnetic field.
Dear Savita Pannu,
If you are looking for better proof or evidence of your magnetic samples and confirm their superparamagnetic behavior, I suggest that you take first-order reversal curve (FORC) analysis. We perform this analysis and other magnetic measurements for researchers affordably. Please contact me or visit our website if you need more information. Email: [email protected]; https://mdkmag.com/
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