I'm using AGM to do these measurements. The input asks for minimum and max Hu(bias field)/Hc(coercivity) values. I know reversal field Hr = -(Hu +Hc) and applied field Ha = (Hc-Hu). What should be the Hc/Hu in terms of the coercivity/squareness of the major loop to get a good set of FORC's
Thank you. This makes sense. I found out that the interaction fields in my samples ranges between -1600 Oe to 700 Oe.
The optimal (Hu, Hc) parameters for a FORC depend a lot on the sample that you are working on, but as you measure more and more you will get a better feel.
I have measured hundreds of FORC diagrams on a broad range of natural samples (rocks and sediments) . What I have found is that 2-3 times the coercivity of the hysteresis loop is usually a good starting point for the maximum Hc. If you know your sample has significant contribution from magnetically hard minerals, then 2-3 time Hcr from a backfield demagnetization of Mrs tends to be better.
For Hu, I generally set it to +/- half the maximum Hc. This produces a square diagram and usually covers the whole region of interest.
Other factors, such as resolution, are also important to consider depending on the use of the diagram (and how much time you want to spend measuring!).
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