Remanence
Remanence or remanent magnetization or residual magnetism is the
The equivalent term residual magnetization is generally used in engineering applications. In
Sometimes the term retentivity is used for remanence measured in units of
Types
Saturation remanence
The default definition of magnetic remanence is the magnetization remaining in zero field after a large magnetic field is applied (enough to achieve
In engineering applications the residual magnetization is often measured using a
Isothermal remanence
Often a single measure of remanence does not provide adequate information on a magnet. For example, magnetic tapes contain a large number of small magnetic particles (see magnetic storage), and these particles are not identical. Magnetic minerals in rocks may have a wide range of magnetic properties (see rock magnetism). One way to look inside these materials is to add or subtract small increments of remanence. One way of doing this is first demagnetizing the magnet in an AC field, and then applying a field H and removing it. This remanence, denoted by Mr(H), depends on the field.[5] It is called the initial remanence[6] or the isothermal remanent magnetization (IRM).[7]
Another kind of IRM can be obtained by first giving the magnet a saturation remanence in one direction and then applying and removing a magnetic field in the opposite direction.[5] This is called demagnetization remanence or DC demagnetization remanence and is denoted by symbols like Md(H), where H is the magnitude of the field.[8] Yet another kind of remanence can be obtained by demagnetizing the saturation remanence in an ac field. This is called AC demagnetization remanence or alternating field demagnetization remanence and is denoted by symbols like Maf(H).
If the particles are noninteracting single-domain particles with uniaxial anisotropy, there are simple linear relations between the remanences.[5]
Anhysteretic remanence
Another kind of laboratory remanence is anhysteretic remanence or anhysteretic remanent magnetization (ARM). This is induced by exposing a magnet to a large alternating field plus a small DC bias field. The amplitude of the alternating field is gradually reduced to zero to get an anhysteretic magnetization, and then the bias field is removed to get the remanence. The anhysteretic magnetization curve is often close to an average of the two branches of the
Examples
This section needs expansion. You can help by adding to it. (September 2016) |
Material | Remanence | References |
---|---|---|
Ferrite (magnet) | 0.35 T (3,500 G) | [14] |
Samarium-cobalt magnet |
0.82–1.16 T (8,200–11,600 G) | [15] |
AlNiCo 5 |
1.28 T (12,800 G) | |
Neodymium magnet | 1–1.3 T (10,000–13,000 G) | [15] |
Steels | 0.9–1.4 T (9,000–14,000 G) | [16][17] |
See also
Notes
- ^ a b Chikazumi 1997
- hard magnet.
- ^ "remanence | Origin and meaning of remanence by Online Etymology Dictionary". www.etymonline.com. Retrieved 2020-01-20.
- ^ "Magnetic Tape Storage and Handling".
- ^ a b c Wohlfarth 1958
- ^ McCurrie & Gaunt 1966
- ^ Néel 1955
- ^ Pfeiffer 1990
- ^ Bozorth 1993
- ^ Jiles & Atherton 1986
- ^ Nowicki 2018
- ^ Jaep 1969
- ^ Banerjee & Mellema 1974
- ^ "Amorphous Magnetic Cores". Hill Technical Sales. 2006. Retrieved 18 January 2014.
- ^ ISBN 978-0-470-69516-6.
- ^ "COBALT: Essential to High Performance Magnetics" (PDF). Arnold Magnetic Technologies. 2012.
- ISBN 978-0-07-366009-7.
References
- Banerjee, S. K.; Mellema, J. P. (1974). "A new method for the determination of paleointensity from the A.R.M. properties of rocks". Earth Planet. Sci. Lett. 23 (2): 177–184. .
- Bozorth, Richard M. (1993) [Reissue of 1951 publication]. Ferromagnetism. AN IEEE Press Classic Reissue. ISBN 0-7803-1032-2.
- Chikazumi, Sōshin (1997). Physics of Ferromagnetism. ISBN 0-19-851776-9.
- Jaep, W. F. (1969). "Anhysteretic magnetization of an assembly of single-domain particles". J. Appl. Phys. 40 (3): 1297–1298. .
- Jiles, D. C.; Atherton, D. L. (1986). "Theory of ferromagnetic hysteresis". J. Magn. Magn. Mater. 61 (1–2): 48–60. .
- McCurrie, R. A.; Gaunt, P. (1966). "The magnetic properties of platinum cobalt near the equiatomic composition part I. the experimental data". Phil. Mag. 13 (123): 567–577. .
- Néel, Louis (1955). "Some theoretical aspects of rock magnetism" (PDF). Adv. Phys. 4 (14): 191–243. .
- Nowicki, M. (2018). "Anhysteretic Magnetization Measurement Methods for Soft Magnetic Materials". Materials. 11 (10): 2021. PMID 30340358.
- Pfeiffer, H. (1990). "Determination of anisotropy field distribution in particle assemblies taking into account thermal fluctuations". Physica Status Solidi. 118 (1): 295–306. .
- Wohlfarth, E. P. (1958). "Relations between different modes of acquisition of the remanent magnetization of ferromagnetic particles". J. Appl. Phys. 29 (3): 595–596. .