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Topic: Magnetic hysteresis

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Hysteresis

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Massachusetts Institute of Technology

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	Hysteresis - Wikipedia, the free encyclopedia
		Hysteresis is a property of systems (usually physical systems) that do not instantly follow the forces applied to them, but react slowly, or do not return completely to their original state: that is, systems whose states depend on their immediate history.
		Hysteresis phenomena occur in magnetic and ferromagnetic materials, as well as in the elastic and electromagnetic behavior of materials, in which a lag occurs between the application and the removal of a force or field and its subsequent effect.
		Hysteresis loop: magnetic flux density (B) as function of magnetic field strength (H) The relationship between magnetic field strength (H) and magnetic flux density (B) is not linear in such materials.
	en.wikipedia.org /wiki/Hysteresis (1484 words)

	Hysteresis (Site not responding. Last check: 2007-10-15)
		Hysteresis is a property of physical systems that do notinstantly follow the forces applied to them, but react slowly, or do not return completely to their original state: that is,systems whose states depend on their immediate history.
		Hysteresis phenomena occur in magnetic and ferromagnetic materials, as well as in the elastic and electromagnetic behavior of materials, in which a lag occurs betweenthe application and the removal of a force or field and its subsequent effect.
		Hysteresis was initially seen only as a problem, but is now considered to be of great importance in technology, and theproperty is used for example when constructing permanentmemory for computers.
	www.therfcc.org /hysteresis-176600.html (876 words)

	Hysteresis in magnetic materials
		The lack of retraceability of the magnetization curve is the property called hysteresis and it is related to the existence of magnetic domains in the material.
		It is customary to plot the magnetization M of the sample as a function of the magnetic field strength H, since H is a measure of the externally applied field which drives the magnetization.
		Because of hysteresis, an input signal at the level indicated by the dashed line could give a magnetization anywhere between C and D, depending upon the immediate previous history of the tape (i.e., the signal which preceded it).
	hyperphysics.phy-astr.gsu.edu /hbase/solids/hyst.html (315 words)

	Hysteresis
		Hysteresis is a property of physical systems that do not instantly follow the forces applied to them, but react slowly, or do not return completely to their original state: that is, systems whose states depend on their immediate history.
		As the magnetic field increases, the magnetization also increases, but it has a lower value than the equilibrium magnetization.
		Electrical hysteresis typically occurs in ferroelectric material, where domainss of polarisation contribute to the total polarisation.
	www.brainyencyclopedia.com /encyclopedia/h/hy/hysteresis.html (958 words)

	Hysteresis (Site not responding. Last check: 2007-10-15)
		Hysteresis is a property of physical systems that do not instantly follow forces applied to them but react slowly do not return completely to their original that is systems whose states depend on immediate history.
		Hysteresis phenomena occur in magnetic and ferromagnetic materials as well as in the elastic and electromagnetic behavior of materials in which a occurs between the application and the removal a force or field and its subsequent effect.
		Hysteresis was initially seen only as a but is now considered to be of importance in technology and the property is for example when constructing permanent memory for computers.
	www.freeglossary.com /Hysteresis (969 words)

	Magnetic hysteresis driven recording element and method
		A magnetic field is applied to a recording element by energization of an electromagnet or by a permanent magnet to a saturation point of the element material to cause the recording element to move in relation to the electromagnet or to the permanent magnet when the magnetic field is reversed.
		The present invention relates to magnetic hysteresis effects and more particularly, to induced repulsion due to magnetic hysteresis wherein the magnetic hardness of the material is a measure of the magnetic field intensity required to saturate the material in relation to the field intensity generated within the material.
		The initial energization of the magnetic field generates a flux which flows through the adjacent impact member or hammer in an amount or magnitude to cause magnetic saturation of the material in the hammer and to tend to draw the hammer toward the flux generating means.
	www.freepatentsonline.com /4221163.html (3450 words)

	Biasing in Magnetic Tape Recording
		The necessity for biasing has its origin in the magnetic property called hysteresis - the magnetic material tends to hold onto any magnetization it receives and must be actively driven back to zero to start over.
		Magnetic emulsions made with chromium dioxide require a larger biasing signal to make use of their wider dynamic range, so modern recorders have different bias settings for iron oxide, chromium dioxide, and metal tapes.
		With optimum biasing, the recorded magnetic image is proportional to the signal current applied to the record head.
	hyperphysics.phy-astr.gsu.edu /hbase/audio/bias.html (365 words)

	Stepper motor magnetic hysteresis correction using a stepping algorithm
		The magnetic hysteresis or magnetic memory error in a stepper motor is erased by sequencing the motor phases in a particular manner.
		Hysteresis is the lag of magnetization behind magnetizing force as the magnetic condition of a ferromagnetic material is changed.
		Briefly, in accordance with this invention, the magnetic hysteresis or magnetic memory error in a stepper motor is erased by sequencing the motor phases in a particular manner.
	www.freepatentsonline.com /4768115.html (3019 words)

	Magnetic hysteresis from the geometrical barrier in type-II superconducting strips (Site not responding. Last check: 2007-10-15)
		Magnetic hysteresis from the geometrical barrier in type-II superconducting strips
		The magnetization is found to be nearly inversely proportional to the applied field upon flux entry and to be proportional to the applied field upon flux exit.
		With bulk pinning, the vortices pile up in two symmetric dome-shaped magnetic flux profiles, within which the current density is equal to the critical current density, whereas the regions near the center and the edges of the strip remain vortex-free.
	cmp.ameslab.gov /cmp/Abstracts/clem_2.html (212 words)

	Apparatus for positioning a takeup reel to receive the lead end of a web
		According to another aspect of the present invention, the effect of a magnetic hysteresis brake which is coupled to the takeup reel when it is rotated by the brushless DC motor in a supply direction is compensated for, so that the reel is brought to the predetermined web takeup position.
		Magnetic tape 14 is transported between reels 12 and 22 by takeup brushless DC motor 28, which is directly connected to hub 20 by means of shaft 30, and a supply brushless DC motor 32, which is directly connected to hub 34 of supply reel 12 by shaft 36.
		2, takeup magnetic hysteresis brake 52 includes a hub 78, rotatably mounted on shaft 30 by means of bearings 80 and 82; a magnetic hysteresis disc 84 mounted on hub 78; and a stationary permanent magnet 86 mounted on magnetic plate 88 (secured to the housing of motor 28).
	www.freepatentsonline.com /4776528.html (2358 words)

	Magnetic Hysteresis:0780360419:Edward Della Torre :eCampus.com
		Electrical Engineering Magnetic Hysteresis Understanding magnetic hysteresis is vitally important to the development of the science of magnetism as a whole and to the advancement of practical magnetic device applications.
		Magnetic Hysteresis, by acclaimed expert Edward Della Torre, presents a clear explanation of the connection between physical principles and phenomenological hysteresis.
		Magnetic Hysteresis is indispensable reading for engineers, physicists, and materials scientists who want to gain a better understanding of hysteresis losses and create more energy-efficient motor designs.
	www.ecampus.com /bk_detail.asp?isbn=0780360419&referrer=yah04 (195 words)

	\vspace{-20mm}\pretitle \\[20mm] \lbf\ti
		Magnetic hysteresis is a topic of great technological interest that has been investigated intensively during the past [1].
		Hysteresis is a complex non-equilibrium phenomenon due to the presence of metastable states in which the system can be trapped for long times.
		The connection between relaxation and hysteresis in disordered magnetic materials is particularly important from both purely theoretical, reflecting the complexity of the free energy landscape, and experimental reasons, since it is essential to understand to which extent recorded information can fade away through thermal relaxation.
	dftpc6.ts.infn.it /pais2001/pa/zapperi.html (2709 words)

	Rimtec Corporation - Magnetic Clutches
		Torque is produced by the magnetic field across the air gap between the two cylinders.
		The torque is produced by the magnetic field across the air gap between the two sections of the clutch.
		In case of overload, hysteresis magnetic clutches disengage without the abrasion and jerks that limit the wear life of conventional mechanical-type clutches.
	www.rimteccorporation.com /products/magnetic (539 words)

	Hysteresis and magnetic susceptibility (from rock) -- Encyclopædia Britannica (Site not responding. Last check: 2007-10-15)
		Hysteresis is the variation of magnetization with applied field and illustrates the ability of a material to retain its magnetization, even after an applied field is removed.
		The magnetic susceptibility of a material, commonly symbolized by, is equal to the ratio of the magnetization M within the material to the applied magnetic field strength H, or = M/H. This ratio, strictly speaking, is the volume susceptibility,...
		When ferromagnetic materials are placed within a coil of wire carrying an electric current, the magnetizing field, or magnetic field strength H, caused by the current forces some or all of the atomic magnets in the material to align with the field.
	www.britannica.com /eb/article?tocId=80201 (895 words)

	Magnetic Hystersis
		Illustrated in the first quadrant of the loop is the initial magnetisation curve (dotted line), which shows the increase in polarisation (and induction) on the application of a field to an unmagnetised sample.
		For a hard magnetic material it is desirable that the domains cannot easily rotate its direction of magnetisation and that the domain walls do not move easily and / or nucleation of domains is difficult.
		Nucleation controlled permanent magnets are easily magnetised as the initial state has several domains in each crystal, but are difficult to demagnetise because this would require the nucleation of new reverse domains.
	www.aacg.bham.ac.uk /magnetic_materials/hysteresis.htm (1075 words)

	Hysteresis in Magnetism
		The interest in hysteresis and magnetism is shared by scientists with an impressive variety of different backgrounds.
		Hysteresis is the central feature of ferromagnetic materials below the Curie temperature, and physicists are still in search of a convincing general theory to interpret it.
		At the same time, hysteresis is the property that engineers exploit in practically all applications of magnetic materials, [...] and there is a widespread need for reliable hysteresis models to be included in design tools.
	www.ien.it /%7Ebertotti/him.htm (180 words)

	PHSX 222L (Site not responding. Last check: 2007-10-15)
		Object: To plot a hysteresis curve for a steel ring, and determine the coercive force and the retentivity for the sample used.
		Once the magnetic material in the core has been fully magnetized, the current in the windings can be turned off, and there will remain a certain amount of magnetization in the material.
		From your plot of the hysteresis curve, identify the value of the retentivity and the coercive force (put the origin at the center of the hysteresis loop).
	www.snow.edu /~larrys/PHSX222L/PHSX222LLabs/Hysteresis.html (616 words)

	AllRefer.com - hysteresis (Electrical Engineering) - Encyclopedia (Site not responding. Last check: 2007-10-15)
		The area of the loop is proportional to the energy dissipated as heat when the system goes through a cycle; this represents a considerable energy loss in alternating-current machinery.
		Thermal hysteresis occurs when the value of a given property of a body depends not only on the body's temperature but also on whether the temperature is rising or falling.
		Unlike the previous examples, this hysteresis effect is not naturally occurring; it is designed into the control system to prevent the damage to the system that would arise from switching on and off too frequently.
	reference.allrefer.com /encyclopedia/H/hysteres.html (405 words)

	NL41
		Magnetic hysteresis is not something one usually worries about when paying the electricity bill, yet it is a fundamental property of the magnetic materials found in electric motors we use at home and the transformers that supply us with current.
		Magnetic hysteresis is responsible for some of the inefficiency in these and other devices.
		In it he reflected a light spot from a mirror whose movements were controlled by the hysteresis of the material.
	www.abdn.ac.uk /~nph126/items/nl41.htm (211 words)

	Encyclopedia of 20th Century Technology -- Sample Entries (Site not responding. Last check: 2007-10-15)
		Coherers and magnet materials were not in themselves detectors, but acted in conjunction with other circuit elements to render radio waves sensible to human beings, producing visible or audible signals.
		Magnetic detectors fell into two broad groups - electrodynamic detectors, in which the presence of a radio signal was shown by the movement of a needle or a mirror, or magnetic hysteresis detectors in which the oscillatory field due to an aerial current changed the state of magnetisation of a piece of ferromagnetic material.
		Any oscillating decreasing currents in the aerial coil would tend to move the iron to a magnetisation state corresponding to the path 0-1, the change would be heard as a signal in the earphone via the shorter secondary coil surrounding the wire.
	tech.routledge-ny.com /detectors.html (1121 words)

	Theory of hysteresis in magnetic ultrathin films (Site not responding. Last check: 2007-10-15)
		For films that are one or two monolayers thick and in which the magnetization lies in plane, the important energies in the problem are the exchange interaction between magnetizations at neighboring sites, the intrinsic anisotropy of the surface and the two-fold anisotropy induced by step edges.
		The coercive field is the field at which the magnetization passes through zero in the hysteresis loop.
		In the model considered here, the coercive field depends on the size of the islands, L, compared to their separation, D, and the domain wall width on the flat surface, W. This figure shows the ratio of the coercive field to the coercive field in the absence of steps as a function of these lengths.
	physics.nist.gov /Divisions/Div841/Gp3/Projects/Theory/theory_hysteresis.html (620 words)

	PIRA 5G40.00 HYSTERESIS (Site not responding. Last check: 2007-10-15)
		The hysteresis loop for the iron core of a transformer is shown on a oscilloscope.
		A small mirror on a compass needle is used to detect the magnetic field as the current to a solenoid containing an iron bar is increased and decreased stepwise.
		The hysteresis loop of a sample placed in one deflection coil is traced on an old TV tube.
	www.physics.ncsu.edu /pira/5eandm/5G40.html (263 words)

	Session J19 - Magnetic Modeling I.
		The hysteresis properties are governed by a combination of the intrinsic properties of the material, such as saturation polarization, magnetic exchange and magnetocrystalline anisotropy.
		Layered magnetic compounds exhibit a variety of interesting experimental properties, among them being the observation of quasi two dimensional order which is influenced by the detailed crystal structure and chemistry.
		The model treats the alternating layers of magnetic and nonmagnetic material as parallel paths for the current flow and treats the magnetic islands formed in discon- tinuous multilayers as being in series.
	flux.aps.org /meetings/YR97/BAPSMAR97/abs/S2490.html (1696 words)

	hysteresis - Hutchinson encyclopedia article about hysteresis
		Phenomenon seen in the elastic and electromagnetic behaviour of materials, in which a lag occurs between the application or removal of a force or field and its effect.
		If the magnetic field applied to a magnetic material is increased and then decreased back to its original value, the magnetic field inside the material does not return to its original value.
		This behaviour results in a loss of energy, called the hysteresis loss, when a sample is repeatedly magnetized and demagnetized.
	encyclopedia.farlex.com /hysteresis (223 words)

	Magnetic Hysteresis of Polycrystalline FeNi Invar Films MOKE and MCD (Site not responding. Last check: 2007-10-15)
		The magnetization reversal of polycrystalline FeNi films grown on glass have been analyzed by magneto-optical Kerr effect in the visible regime and element-specific circular dichroism at the 2p thresholds of Fe and Ni.
		For magnetization not parallel to a soft direction, reversal proceeds via rotation of the magnetization towards the soft direction, and formation of 180 domains.
		Similar anomalies are observed also in the MCD hysteresis loops, however, in one case only in the Fe loop, but not in the Ni loop.
	schulzeundschultze.anphy.uni-duesseldorf.de /termine/workshop/abs9.phtml (200 words)

	IEEE Magnetics Society Newsletter
		Emphasis is placed on experimental and theoretical research in magnetism, the properties and synthesis of new magnetic materials, and advances in magnetic technology.
		The 5th International Symposium on Hysteresis and Micromagnetic Modeling is devoted to the 100 year anniversary of birth of Hungarian scientist F. Preisach, the creator of the hysteresis model, bearing his name.
		The aim of the 5th International Symposium on Hysteresis and Micromagnetic Modeling is intended to be a forum for presentation and discussion of the most recent advancements in the fields of hysteresis modeling and computational micromagnetics.
	www.ieeemagnetics.org /Newsletter/oct04/conference.htm (666 words)

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