What is the physical meaning of "Recoil Permeability"

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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?



1 Reply Last Post Apr 16, 2021, 6:59 PM EDT
Robert Koslover Antennas, Waveguides, Electromagnetics

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Posted: 4 weeks ago Apr 16, 2021, 6:59 PM EDT
Updated: 4 weeks ago Apr 16, 2021, 7:09 PM EDT

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).

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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