In materials scienceGiant Magnetoimpedance (GMI) is the effect that occurs in some materials where an external magnetic field causes a large variation in the electrical impedance of the material. It should not be confused with the separate physical phenomenon of Giant Magnetoresistance.
GMI is caused by the penetration length that is a measure of how deep an ac electrical current can flow inside an electrical conductor. The penetration length (also known as the skin-depth effect) increases with the square root of the electrical resistivity of the material and is inversely proportional to the square root of the product of the magnetic permeability and the frequency of the ac electrical current. Thus, in materials with very high values of magnetic permeability, such as soft-ferromagnetic materials, the penetration-length can be much less than the thickness of the conductor even for moderate values of frequencies driving the current near the surface of the material.
When an external magnetic field is applied, the size of the permeability diminishes, increasing the penetration of the current in the magnetic material. Large variations are observed in both in-phase and out-of-phase components of the magnetoimpedance for applied magnetic fields close to the value of the Earth magnetic field up to few tens of Oersted. For comparison, in normal electrical conductors the effect of the skin-depth becomes important for frequencies in the microwave range only.
Despite the fact that the dependence of the GMI on the geometry of the electrical conductor (ribbons, wires, multilayers meander-likes) and external parameters is somewhat complex, there are theoretical models that allow calculation of the GMI to within some approximations.[1][2] Beside the dependence of the GMI on the frequency of the current there are other sources that contribute to the frequency dependence of the GMI, such as the motion of the domain wall and the ferromagnetic resonance.[3]
Experimental measurementedit
A typical experimental set-up for investigating the GMI in research laboratories is shown below. It includes an alternating current source, a phase sensitive amplifier for detecting the ac voltage across the sample and an electromagnet for applying a dc magnetic field. A cryostat or an oven may be required for measuring the temperature dependence of the GMI.[4]
Typical experimental set-up for measuring the GMI (inset) and GMI data for a FeZr alloy at 150 K (From ref. 4).
Several experimental measurements were also performed to characterize the long-term stability and the thermal drift of the GMI, which were supported by a theoretical model describing the physical modeling of the sensing element.[5]
Historyedit
The observation that the impedance of soft-magnetic materials is influenced by the frequency and amplitudes of applied magnetic fields was first observed in the 1930s.[6][7] These initial studies were limited to frequencies of a few hundreds of Hz and the changes of impedance reported in those works were not large. Starting in the 1990s, this phenomenon was investigated again, this time making use of currents with frequencies of hundreds of kHz.[8]
Because of the huge variations observed in the magnetic field dependence of the magnetoimpedance it was named giant magnetoimpedance.[9] Due to the high sensitivity of the sensors using the GMI effect, they have been used in compasses, accelerometers, virus detection, biomagnetism, among other applications.[10][11][12]
In-phase component of the GMI measured for a piece of an amorphous ferromagnetic material (From ref. 7)
Referencesedit
^Machado; et al. (1996-04-15). "A theoretical model for the giant magnetoimpedance in ribbons of amorphous soft‐ferromagnetic alloys". Journal of Applied Physics. 79 (8): 6558–6560. Bibcode:1996JAP....79.6558M. doi:10.1063/1.361945. ISSN 0021-8979.
^Panina; et al. (1995-03-01). "Giant magneto-impedance in Co-rich amorphous wires and films". IEEE Transactions on Magnetics. 31 (2): 1249–1260. Bibcode:1995ITM....31.1249P. doi:10.1109/20.364815. ISSN 0018-9464.
^Machado; et al. (1999). "Surface Magnetoimpedance Measurements in Soft-Ferromagnetic Materials". Physica Status Solidi A. 173 (1): 135–144. Bibcode:1999PSSAR.173..135M. doi:10.1002/(SICI)1521-396X(199905)173:1<135::AID-PSSA135>3.0.CO;2-#.
^Ribeiro; et al. (2016-09-05). "GMI in the reentrant spin-glass Fe90Zr10 alloy: Investigation of the spin dynamics in the MHz frequency regime". Applied Physics Letters. 109 (10): 102404. Bibcode:2016ApPhL.109j2404R. doi:10.1063/1.4962534. ISSN 0003-6951. OSTI 1467896.
^Esper; et al. (2020-08-15). "Theoretical and Experimental Investigation of Temperature-Compensated Off-Diagonal GMI Magnetometer and Its Long-Term Stability". IEEE Sensors Journal. 20: 9046-9055. doi:10.1109/JSEN.2020.2988939. S2CID 219091478.
^HARRISON, E. P.; TURNEY, G. L.; ROWE, H. (1935). "Electrical Properties of Wires of High Permeability". Nature. 135 (3423): 961. Bibcode:1935Natur.135..961H. doi:10.1038/135961a0. S2CID 4137307.
^Harrison, E. P.; Turney, G. L.; Rowe, H.; Gollop, H. (1936-11-02). "The Electrical Properties of High Permeability Wires Carrying Alternating Current". Proceedings of the Royal Society of London A: Mathematical, Physical and Engineering Sciences. 157 (891): 451–479. Bibcode:1936RSPSA.157..451H. doi:10.1098/rspa.1936.0208. ISSN 1364-5021.
^Machado; et al. (1994-05-15). "Giant ac magnetoresistance in the soft ferromagnet Co70.4Fe4.6Si15B10". Journal of Applied Physics. 75 (10): 6563–6565. Bibcode:1994JAP....75.6563M. doi:10.1063/1.356919. ISSN 0021-8979.
^Panina; et al. (1994-11-15). "Giant magneto‐impedance and magneto‐inductive effects in amorphous alloys (invited)". Journal of Applied Physics. 76 (10): 6198–6203. Bibcode:1994JAP....76.6198P. doi:10.1063/1.358310. ISSN 0021-8979.
^Knobel, M.; Vazquez, M.; Kraus, L. (2003). Buschow, K.H.J. (ed.). Giant Magnetoimpedance in Handbook of magnetic materials. The Netherlands: Elsevier. pp. 497–564. ISBN978-0-444-51459-2.
^Knobel, M.; Pirota, K. R. (2002-04-01). "Giant magnetoimpedance: concepts and recent progress". Journal of Magnetism and Magnetic Materials. Proceedings of the Joint European Magnetic Symposia (JEMS'01). 242–245, Part 1: 33–40. Bibcode:2002JMMM..242...33K. doi:10.1016/S0304-8853(01)01180-5.
^Phan, Manh-Huong; Peng, Hua-Xin (2008-02-01). "Giant magnetoimpedance materials: Fundamentals and applications". Progress in Materials Science. 53 (2): 323–420. doi:10.1016/j.pmatsci.2007.05.003.
April 14, 2024
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In materials science Giant Magnetoimpedance GMI is the effect that occurs in some materials where an external magnetic field causes a large variation in the electrical impedance of the material It should not be confused with the separate physical phenomenon of Giant Magnetoresistance Contents 1 The phenomenology of the GMI 2 Experimental measurement 3 History 4 ReferencesThe phenomenology of the GMI editGMI is caused by the penetration length that is a measure of how deep an ac electrical current can flow inside an electrical conductor The penetration length also known as the skin depth effect increases with the square root of the electrical resistivity of the material and is inversely proportional to the square root of the product of the magnetic permeability and the frequency of the ac electrical current Thus in materials with very high values of magnetic permeability such as soft ferromagnetic materials the penetration length can be much less than the thickness of the conductor even for moderate values of frequencies driving the current near the surface of the material When an external magnetic field is applied the size of the permeability diminishes increasing the penetration of the current in the magnetic material Large variations are observed in both in phase and out of phase components of the magnetoimpedance for applied magnetic fields close to the value of the Earth magnetic field up to few tens of Oersted For comparison in normal electrical conductors the effect of the skin depth becomes important for frequencies in the microwave range only Despite the fact that the dependence of the GMI on the geometry of the electrical conductor ribbons wires multilayers meander likes and external parameters is somewhat complex there are theoretical models that allow calculation of the GMI to within some approximations 1 2 Beside the dependence of the GMI on the frequency of the current there are other sources that contribute to the frequency dependence of the GMI such as the motion of the domain wall and the ferromagnetic resonance 3 Experimental measurement editA typical experimental set up for investigating the GMI in research laboratories is shown below It includes an alternating current source a phase sensitive amplifier for detecting the ac voltage across the sample and an electromagnet for applying a dc magnetic field A cryostat or an oven may be required for measuring the temperature dependence of the GMI 4 nbsp Typical experimental set up for measuring the GMI inset and GMI data for a FeZr alloy at 150 K From ref 4 Several experimental measurements were also performed to characterize the long term stability and the thermal drift of the GMI which were supported by a theoretical model describing the physical modeling of the sensing element 5 History editThe observation that the impedance of soft magnetic materials is influenced by the frequency and amplitudes of applied magnetic fields was first observed in the 1930s 6 7 These initial studies were limited to frequencies of a few hundreds of Hz and the changes of impedance reported in those works were not large Starting in the 1990s this phenomenon was investigated again this time making use of currents with frequencies of hundreds of kHz 8 Because of the huge variations observed in the magnetic field dependence of the magnetoimpedance it was named giant magnetoimpedance 9 Due to the high sensitivity of the sensors using the GMI effect they have been used in compasses accelerometers virus detection biomagnetism among other applications 10 11 12 nbsp In phase component of the GMI measured for a piece of an amorphous ferromagnetic material From ref 7 References edit Machado et al 1996 04 15 A theoretical model for the giant magnetoimpedance in ribbons of amorphous soft ferromagnetic alloys Journal of Applied Physics 79 8 6558 6560 Bibcode 1996JAP 79 6558M doi 10 1063 1 361945 ISSN 0021 8979 Panina et al 1995 03 01 Giant magneto impedance in Co rich amorphous wires and films IEEE Transactions on Magnetics 31 2 1249 1260 Bibcode 1995ITM 31 1249P doi 10 1109 20 364815 ISSN 0018 9464 Machado et al 1999 Surface Magnetoimpedance Measurements in Soft Ferromagnetic Materials Physica Status Solidi A 173 1 135 144 Bibcode 1999PSSAR 173 135M doi 10 1002 SICI 1521 396X 199905 173 1 lt 135 AID PSSA135 gt 3 0 CO 2 Ribeiro et al 2016 09 05 GMI in the reentrant spin glass Fe90Zr10 alloy Investigation of the spin dynamics in the MHz frequency regime Applied Physics Letters 109 10 102404 Bibcode 2016ApPhL 109j2404R doi 10 1063 1 4962534 ISSN 0003 6951 OSTI 1467896 Esper et al 2020 08 15 Theoretical and Experimental Investigation of Temperature Compensated Off Diagonal GMI Magnetometer and Its Long Term Stability IEEE Sensors Journal 20 9046 9055 doi 10 1109 JSEN 2020 2988939 S2CID 219091478 HARRISON E P TURNEY G L ROWE H 1935 Electrical Properties of Wires of High Permeability Nature 135 3423 961 Bibcode 1935Natur 135 961H doi 10 1038 135961a0 S2CID 4137307 Harrison E P Turney G L Rowe H Gollop H 1936 11 02 The Electrical Properties of High Permeability Wires Carrying Alternating Current Proceedings of the Royal Society of London A Mathematical Physical and Engineering Sciences 157 891 451 479 Bibcode 1936RSPSA 157 451H doi 10 1098 rspa 1936 0208 ISSN 1364 5021 Machado et al 1994 05 15 Giant ac magnetoresistance in the soft ferromagnet Co70 4Fe4 6Si15B10 Journal of Applied Physics 75 10 6563 6565 Bibcode 1994JAP 75 6563M doi 10 1063 1 356919 ISSN 0021 8979 Panina et al 1994 11 15 Giant magneto impedance and magneto inductive effects in amorphous alloys invited Journal of Applied Physics 76 10 6198 6203 Bibcode 1994JAP 76 6198P doi 10 1063 1 358310 ISSN 0021 8979 Knobel M Vazquez M Kraus L 2003 Buschow K H J ed Giant Magnetoimpedance in Handbook of magnetic materials The Netherlands Elsevier pp 497 564 ISBN 978 0 444 51459 2 Knobel M Pirota K R 2002 04 01 Giant magnetoimpedance concepts and recent progress Journal of Magnetism and Magnetic Materials Proceedings of the Joint European Magnetic Symposia JEMS 01 242 245 Part 1 33 40 Bibcode 2002JMMM 242 33K doi 10 1016 S0304 8853 01 01180 5 Phan Manh Huong Peng Hua Xin 2008 02 01 Giant magnetoimpedance materials Fundamentals and applications Progress in Materials Science 53 2 323 420 doi 10 1016 j pmatsci 2007 05 003 Retrieved from https en wikipedia org w index php title Giant magnetoimpedance amp oldid 1136305842, wikipedia, wiki, book, books, library,
