 Founding results of Fert et al. The Giant Magnetoresistance (GMR) is a quantum mechanical effect observed in thin film structures composed of alternating ferromagnetic and nonmagnetic metal layers. Image File history File links GMR.svg Summary ((fr)) Schéma illustrant les résultats de léquipe dA. Fert en 1998 à Orsay. ...
Image File history File links GMR.svg Summary ((fr)) Schéma illustrant les résultats de léquipe dA. Fert en 1998 à Orsay. ...
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Ferromagnetism is a phenomenon by which a material can exhibit a spontaneous magnetization, and is one of the strongest forms of magnetism. ...
The effect manifests itself as a significant decrease in resistance from the zero-field state, when the magnetization of adjacent ferromagnetic layers are antiparallel due to a weak anti-ferromagnetic coupling between layers, to a lower level of resistance when the magnetization of the adjacent layers align due to an applied external field. The spin of the electrons of the nonmagnetic metal align parallel or antiparallel with an applied magnetic field in equal numbers, and therefore suffer less magnetic scattering when the magnetizations of the ferromagnetic layers are parallel. In physics, spin refers to the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its center of mass about an external point. ...
Properties The electron (also called negatron, commonly represented as e−) is a subatomic particle. ...
Discovery GMR was independently discovered in 1988 in Fe/Cr/Fe trilayers by a research team led by Peter Grünberg of the Jülich Research Centre, who owns the patent, and in Fe/Cr multilayers by the group of Albert Fert of the University of Paris-Sud, who first saw the large effect in multilayers that led to its naming, coined the name, and first correctly explained the underlying physics. The discovery of GMR is considered as the birth of spintronics. Peter Grünberg and Albert Fert have received a number of prestigious prizes and awards for their discovery and contributions to the field of spintronics. The most recent are the Japan Prize 2007 and the Wolf Prize 2007. Dr Peter Grünberg is a German physicist and one of the discoverers of the Giant magnetoresistive effect which brought about a breakthrough in gigabyte hard disks. ...
Position of Jülich Research Centre in Germany The Jülich Research Centre (German: Forschungszentrum Jülich, short FZJ) is based near Jülich, North Rhine-Westphalia, Germany. ...
Professor Albert Fert is a French physicist, and one of the discoverers of the Giant magnetoresistive effect which brought about a breakthrough in gigabyte hard disks. ...
Astrophysics building in the campus The University of Paris-Sud (French: Université de Paris-Sud) is a French university located in Orsay, a southern suburb of Paris. ...
Unsolved problems in physics: Is it possible to construct a practical electronic device that operates on the spin of the electron, rather than its charge? Spintronics (a neologism for spin-based electronics), also known as magnetoelectronics, is an emergent technology which exploits a quantum property of electrons known as spin...
Types of GMR
Multilayer GMR Two or more ferromagnetic layers are separated by a very thin (about 1 nm) non-ferromagnetic spacer (e.g. Fe/Cr/Fe). At certain thicknesses the RKKY coupling between adjacent ferromagnetic layers becomes antiferromagnetic, making it energetically preferable for the magnetizations of adjacent layers to align in anti-parallel. The electrical resistance of the device is normally higher in the anti-parallel case and the difference can reach several 10% at room temperature. The interlayer spacing in these devices typically corresponds to the second antiferromagnetic peak in the AFM-FM oscillation in the RKKY coupling. Ferromagnetism is a phenomenon by which a material can exhibit a spontaneous magnetization, and is one of the strongest forms of magnetism. ...
RKKY stands for Ruderman-Kittel-Kasuya-Yosida and refers to a coupling mechanism of nuclear magnetic moments in a metal by means of an interaction with the conduction electrons. ...
The GMR effect was first observed in the multilayer configuration, with much early research into GMR focusing on multilayer stacks of 10 or more layers.
Two ferromagnetic layers are separated by a thin (about 3 nm) non-ferromagnetic spacer, but without RKKY coupling. If the coercive fields of the two ferromagnetic electrodes are different it is possible to switch them independently. Therefore, parallel and anti-parallel alignment can be achieved, and normally the resistance is again higher in the anti-parallel case. This device is sometimes also called spin-valve. A spin valve is a device consisting of two or more conducting magnetic materials, that alternates its electrical resistance (from low to high or high to low) depending on the alignment of the magnetic layers. ...
Image File history File links Spin-valve_GMR.svg Summary (fr) Modèle électrique de la magnétorésistance géante, effet vanne de spin ou spin valve. ...
Image File history File links Spin-valve_GMR.svg Summary (fr) Modèle électrique de la magnétorésistance géante, effet vanne de spin ou spin valve. ...
RKKY stands for Ruderman-Kittel-Kasuya-Yosida and refers to a coupling mechanism of nuclear magnetic moments in a metal by means of an interaction with the conduction electrons. ...
A spin valve is a device consisting of two or more conducting magnetic materials, that alternates its electrical resistance (from low to high or high to low) depending on the alignment of the magnetic layers. ...
spin-valve GMR is the configuration that is most industrially useful, and is the configuration used in hard drives. A spin valve is a device consisting of two or more conducting magnetic materials, that alternates its electrical resistance (from low to high or high to low) depending on the alignment of the magnetic layers. ...
Typical hard drives of the mid-1990s. ...
Granular GMR Granular GMR is an effect that occurs in solid precipitates of a magnetic material in a non-magnetic matrix. In practice, granular GMR is only observed in matrices of copper containing cobalt granules. The reason for this is that copper and cobalt are immiscible, and so it is possible to create the solid precipitate by rapidly cooling a molten mixture of copper and cobalt. Granule sizes vary depending on the cooling rate and amount of subsequent annealing. Granular GMR materials have not been able to produce the high GMR ratios found in the multilayer counterparts. A substance is soluble in a fluid if it dissolves in the fluid. ...
Annealing, in metallurgy and materials science, is a heat treatment wherein the microstructure of a material is altered, causing changes in its properties such as strength and hardness. ...
Applications As stated above, GMR has been used extensively in the read heads in modern hard drives. Another application of the GMR effect is in non-volatile, magnetic random access memory (MRAM). Magnetoresistive Random Access Memory (MRAM) is a non-volatile computer memory (NVRAM) technology, which has been in development since the 1990s. ...
References - Magnetic properties of superlattices formed from ferromagnetic and antiferromagnetic materials, L. L. Hinchey and D. L. Mills, Physical Review B, vol. 33, no. 5, pp 3329, March 1986.
- Layered Magnetic Structures: Evidence for Antiferromagnetic Coupling of Fe Layers across Cr Interlayers, P. Grünberg, R. Schreiber, Y. Pang, M. B. Brodsky, and H. Sowers, Physical Review Letters, vol. 57, no. 19, pp 2442, November, 1986.
- Antiparallel coupling between Fe layers separated by a Cr interlayer: Dependence of the magnetization on the film thickness, C. Carbone and S. F. Alvarado, Physical Review B, vol. 36, no. 4, pp 2433, August 1987.
- Giant Magnetoresistance of (001)Fe/(001)Cr Magnetic Superlattices, M. N. Baibich, J. M. Broto, A. Fert, F. Nguyen Van Dau, F. Petroff, P. Eitenne, g. Creuzet, A. Friederich, and J. Chazelas, Physical Review Letters, vol. 61, no. 21, pp. 2472, November 1988.
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