Dear Leila,

Q1: I do not understand what is the meaning of this question.

Q2: Your curves present the so called switching field distributions. The one calculated or upper branch of hysteresis curve is the distribution of up-switching fields, while the second one (of the same color) illustrates down-switching field distribution. They should be also obtainable by integrating the FORC map (Preisach diagram) along the line down-switching field = constant (this is one-dimensional integration). Such a procedure delivers a single point on your curve.

What can I say about your figure? Both samples ('red' and 'blue') seem to have symmetric and unimodal FORC map, with pretty sharp maximum around 0.6 kOe ('red' sample) and much wider (flat) maximum slightly above 1 kOe for the 'blue' sample. The numbers above should be roughly equal to coercivities of both samples.

Q3: No. dM/dH at H=0 is the so called static susceptibility of your whole sample, not of its small parts.

Q4: It is only possible for samples exhibiting negligible hysteresis (superparamagnetic ones). See my enclosed paper.

Stay healthy,

Marek

Dear Marek

I realy appritiated

Answer:

Q1- dM/dH is the derivative of the magnetization (M) with respect to the applied magnetic field (H). It is a measure of the sensitivity of the magnetization to changes in the applied field.

Q2- FORC diagrams are used to analyze the hysteresis loops of magnetic materials. The dM/dH value is used to calculate the FORC diagrams, which are used to determine the coercivity, remanence, and other properties of the material.

Q3-No, the meaning of dM/dH at (H=0) is not nanoparticle susceptibility. It is the slope of the magnetization curve at the origin, which is a measure of the material's susceptibility to an applied field.

Q4-dM/dH can be used to discuss grain size by examining the shape of the magnetization curve. A steeper slope indicates smaller grains, while a flatter slope indicates larger grains. Additionally, the coercivity of the material can be used to infer grain size, as smaller grains tend to have higher coercivity values.