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What is the physical meaning of "Recoil Permeability"
Posted 16.04.2021, 18:15 GMT-4 Low-Frequency Electromagnetics Version 5.6 1 Reply
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When creating a permanent magnet using an Ampere's Law node (in Magnetic Fields), I have the option to set the "recoil permeability" 
. What is recoil permeability?
From the equation, it looks similar, perhaps, to a relative permeability. But if that were the case, why not just call it "relative?" How do I figure out the value of for the real-life neodymium magnet I am modeling in COMSOL?
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Evidently, it is dB/dH taken along the demagnetization part of the hysteresis curve. It is of relevance whenever M is not constant. See "Permanent Magnet Materials and Their Application," by Peter Campbell, Cambridge Univ. Press, 1994, for a good discussion. On the web, for examples, see among others, https://www.shinetsu-rare-earth-magnet.jp/e/design/words/r_c.html or https://www.arnoldmagnetics.com/wp-content/uploads/2017/10/Hk-A-Key-Magnetic-Figure-of-Merit-TN_0901_rev_160212.pdf or http://maglab.iphy.ac.cn/M05Website/PDF/2008/APL93(2008)182503.pdf for more usage of this concept. Here's what Arnold Magnetics says: "µ(REC) = Recoil permeability is measured on the normal curve. When referring to the corresponding slope on the intrinsic curve it is called the intrinsic recoil permeability. In the cgs-Gaussian system where 1 gauss equals 1 oersted, the intrinsic recoil equals the normal recoil minus 1. For example, a typical rare earth magnet might have a µ(REC) = 1.05 and the Intrinsic µ(REC) = 0.05. " (I don't claim to fully understand this, but I suspect you will need to, if you want to do your work correctly).
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