Giant magnetoresistance
Giant magnetoresistance (GMR) is a very small magnetic effect found in thin layers of iron and other materials. It is used to read and write information in hard drives.
The GMR effect can be measured when a magnet is used to change the flow of electricity. The 2007 Nobel Prize in physics was awarded to Albert Fert and Peter Grünberg for the discovery of GMR.
Discovery change
GMR was discovered in layers iron, chrome and ferrite by Peter Grünbergs research team of the Jülich Research Centre (Germany) in 1988. Peter Grünberg owns a patent for the technology. It was also discovered by Albert Ferts research group of the University of Paris-Sud (France) in layers ferrite and chrome. The Fert group were first to see what they thought of as a large effect which is why they gave the name "Giant". The Fert group were also first to explain the correct physics of GMR. The discovery was the beginning of the science spintronics. Grünberg and Fert have been given prizes and awards, including the 2007 Nobel Prize in Physics, for this discovery and other spintronics work.
Types of GMR change
Multilayer GMR change
In multilayer GMR, two or more magnetic layers are separated by a very thin (about 1 nm) non-magnetic (insulating) layer. Ferrite, a form of iron, is a magnetic layer and chrome is an insulating layer. At certain thickness, the strength of magnetism between the layers becomes easy to measure and adjust. The strength of electrical current between the layers can change by up to 10%.
The GMR effect was first observed in stacks of 10 or more layers.
Spin valve GMR change
In spin valve GMR, two magnetic layers are separated by a thin (~3 nm) non-magnetic (insulating) layer. It is possible to measure and adjust the strength of magnetism between these layers.
It is hoped that research into spinning electrons will improve spin valves.
Materials used in spin valves are copper and an alloy of nickel and iron.
Spin valve GMR is the most useful sort for hard drives and is tested carefully to meet industry standards.
Granular GMR change
Granular GMR is an effect found in copper containing grains of cobalt. It is not possible to control the strength of granular GMR in the same manner as Multilayer GMR.
Use of GMR change
GMR is used in modern hard drives and magnetic sensors. Another use of the GMR effect is in magnetoresistive random access memory (MRAM). GMR has begun a new science of electronics called spintronics.
Related pages change
References change
- L. L. Hinchey and D. L. Mills (1986). "Magnetic properties of superlattices formed from ferromagnetic and antiferromagnetic materials". Physical Review B. 33 (5): 3329–3343. Bibcode:1986PhRvB..33.3329H. doi:10.1103/PhysRevB.33.3329. PMID 9938712.
- P. Grünberg, R. Schreiber, Y. Pang, M. B. Brodsky, and H. Sowers (1986). "Layered Magnetic Structures: Evidence for Antiferromagnetic Coupling of Fe Layers across Cr Interlayers". Physical Review Letters. 57 (19): 2442–2445. Bibcode:1986PhRvL..57.2442G. doi:10.1103/PhysRevLett.57.2442. PMID 10033726.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - C. Carbone and S. F. Alvarado (1987). "Antiparallel coupling between Fe layers separated by a Cr interlayer: Dependence of the magnetization on the film thickness". Physical Review B. 36 (4): 2433–2435. Bibcode:1987PhRvB..36.2433C. doi:10.1103/PhysRevB.36.2433. PMID 9943122.
- M. N. Baibich, J. M. Broto, A. Fert, F. Nguyen Van Dau, F. Petroff, P. Eitenne, G. Creuzet, A. Friederich, and J. Chazelas (1988). "Giant Magnetoresistance of (001)Fe/(001)Cr Magnetic Superlattices". Physical Review Letters. 61 (21): 2472–2475. Bibcode:1988PhRvL..61.2472B. doi:10.1103/PhysRevLett.61.2472. PMID 10039127.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - G. Binasch, P. Grünberg, F. Saurenbach, and W. Zinn (1989). "Enhanced magnetoresistance in layered magnetic structures with antiferromagnetic interlayer exchange". Physical Review B. 39 (7): 4828–4830. Bibcode:1989PhRvB..39.4828B. doi:10.1103/PhysRevB.39.4828. PMID 9948867.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - A. E. Berkowitz, J. R. Mitchell, M. J. Carey, A. P. Young, S. Zhang, F. E. Spada, F. T. Parker, A. Hutten, and G. Thomas (1992). "Giant magnetoresistance in heterogeneous Cu-Co alloys". Physical Review Letters. 68 (25): 3745–3748. Bibcode:1992PhRvL..68.3745B. doi:10.1103/PhysRevLett.68.3745. PMID 10045786.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - John Q. Xiao, J. Samuel Jiang, and C. L. Chien (1992). "Giant magnetoresistance in nonmultilayer magnetic systems". Physical Review Letters. 68 (25): 3749–3752. Bibcode:1992PhRvL..68.3749X. doi:10.1103/PhysRevLett.68.3749. PMID 10045787.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - Z.Y. Leong, S.G. Tan, M.B.A. Jalil, S. Bala Kumar, and G.C. Han (2007). "Magnetoresistance modulation due to interfacial conductance of current perpendicular-to-plane spin valves". Journal of Magnetism and Magnetic Materials. 310 (2): e635–637. Bibcode:2007JMMM..310E.635L. doi:10.1016/j.jmmm.2006.10.679.
{{cite journal}}: CS1 maint: multiple names: authors list (link)
Other websites change
- Giant Magnetoresistance: The Really Big Idea Behind a Very Tiny Tool Archived 2011-05-18 at the Wayback Machine National High Magnetic Field Laboratory
- Presentation of GMR-technique (IBM Research) Archived 2012-01-11 at the Wayback Machine
- Nobel prize in physics 2007 - Scientific background
- Scientific background