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Topic: Exchange bias

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	Magnetoresistive head with enhanced exchange bias field - Patent 5262914
		This bias field is normal to the plane of the magnetic media and parallel to the surface of the planar MR sensor.
		The other bias field which is usually employed with MR sensors is referred to in the art as the longitudinal bias field, which extends parallel to the surface of the magnetic media and parallel to the lengthwise direction of the MR sensor.
		The transverse bias can be produced by a soft magnetic film layer (not shown) which is separated from the MR layer 12 by a thin nonmagnetic spacer layer (not shown) whose purpose is to prevent magnetic exchange between the MR layer 12 and the soft magnetic bias layer as is known in the art.
	www.freepatentsonline.com /5262914.html (2316 words)

	Pinning Down Exchange Bias
		Exchange bias refers to a preferred direction of magnetization of a ferromagnet in contact with an antiferromagnet.
		Magnetic devices based on exchange bias are of considerable commercial importance for data storage, but the mechanism behind it has evaded detection for 50 years.
		Exchange bias provides a magnetic reference, so that the read head can sense binary bits of information as the direction of magnetization in a small area of the disk changes between the two that are allowed.
	www-als.lbl.gov /als/science/sci_archive/78exchange_bias.html (1080 words)

	"GP31C-0098" in fm06
		AB: Magnetic exchange bias is a phenomenon whereby the hysteresis loop of a "soft" magnetic phase is shifted along the applied field axis by an amount of exchange due to interaction with a "hard" magnetic phase.
		Exchange bias is the subject of intense experimental and theoretical investigation because of its widespread technological applications and recent advances in manipulating nanoscale materials.
		Here we discuss a natural sample that has one of the largest exchange biases ever reported, nearly 1 Tesla (T) in a 1.5 T field and is the first documented example of exchange bias of this magnitude in a natural mineral.
	www.agu.org /cgi-bin/wais?hh=GP31C-0098 (319 words)

	[No title]
		The exchange bias phenomenon is due to the interaction between the FM and AF moments at the FM/AF interface via a Heisenberg-like interaction of $\overrightarrow{S}_{FM} \cdot \overrightarrow{S}_{AF}$, where $\overrightarrow{S}_{FM}$ and $\overrightarrow{S}_{AF}$ are the spins of the FM and AF moments respectively.
		In exchange bias, the essential quantity is $\overrightarrow{M}_{FM} \cdot \Delta\overrightarrow{M}_{AF}$, where $\overrightarrow{M}_{FM}$ is the magnetization of the FM and $\Delta\overrightarrow{M}_{AF}$ is the net uncompensated magnetization of the AF at the interface as a result of field cooling.
		The underlying mechanism of the oscillatory exchange bias in (100)Cr/Py is the AF spin structure of the incommensurate SDW in thin Cr layer, schematically shown in Fig.
	www.lava.net /~downes/616/oldtex.txt (2457 words)

	Exchange bias (Site not responding. Last check: 2007-09-23)
		The exchange bias phenomenon is of tremendous utility in magnetic recording, where it is used to pin the state of the readback heads of hard disk drives at exactly their point of maximum sensitivity; hence the term "bias."
		Exchange bias was initially used to stabilize the magnetization of soft ferromagnetic layers in readback heads based on the anisotropic magnetoresistance (AMR) effect.
		Currently exchange bias is used to pin the harder reference layer in spin valve readback heads and MRAM memory circuits that utilize the giant magnetoresistance or magnetic tunneling effect.
	wiki-shorts.freestat.pl /23-1979-Exchange_bias.html (585 words)

	Exchange Bias
		Exchange fields come free of charge and are equivalent to regular magnetic fields in their action on the spin part of the magnetization.
		Historically, the main problem in establishing a realistic model of exchange bias was the lack of information on the spin structure near the all-important interface, and owing to the difficulty of experimentally determining the magnetic structure right near the interface, the exchange bias puzzle remain ed unsolved for nearly 50 years.
		exchange bias and their number is proportional to the size of the bias.
	www-ssrl.slac.stanford.edu /stohr/magneticexchange.htm (4219 words)

	Novel abutted exchange bias design for sensor stabilization patent invention
		By arranging for the flux flow in the free layer to be equal to the flux flow in the adjoining hard bias layer, the demagnetizing field at the junction edges of the aforementioned layers vanishes because of the absence of magnetic poles at the junction.
		M.sub.rt is the component that provides the longitudinal bias flux to the free layer and must be high enough to assure a single magnetic domain in the free layer but not so high as to prevent the magnetic field in the free layer from rotating under the influence of a reasonably sized external magnetic field.
		The hard bias structure is a stack of layers disposed on the substrate and along the sidewalls of a GMR-CIP sensor or on an Al.sub.2O.sub.3 insulation layer in a TMR or GMR-CPP sensor.
	www.freshpatents.com /Novel-abutted-exchange-bias-design-for-sensor-stabilization-dt20060907ptan20060196039.php (2292 words)

	New study shows ferromagnet and anti-ferromagnet alignment colinear
		Exchange bias occurs when the exchange coupling of ferromagnetic and anti-ferromagnetic films across their common interface causes a shift in the hysteresis loop of the ferromagnet.
		Exchange bias is useful in controlling the magnetization in heads used in magnetic disk storage.
		Michael R. Scheinfein, a physics professor at Arizona State University and one of the paper's authors, said by using a polarized x-ray magnetic dichroism spectromicroscopy that separately revealed the micromagnetic structure on both sides of the interface, it was possible to confirm an AFM and FM colinear alignment.
	www.eurekalert.org /pub_releases/2000-06/ASUC-Nssf-1306100.php (304 words)

	Exchange bias - Wikipedia, the free encyclopedia
		Exchange bias or exchange anisotropy occurs in bilayers (or multilayers) of magnetic materials where the hard magnetization behavior of an antiferromagnetic thin film causes a shift in the soft magnetization curve of a ferromagnetic film.
		Exchange anisotropy has long been poorly understood due to the difficulty of studying the dynamics of domain walls in thin antiferromagnetic films.
		The first commercial device to employ the exchange bias was IBM's anisotropic magnetoresistance (AMR) disk drive recording head, which was based on a design by Hunt in the 1970s but which didn't fully displace the inductive readback head until the early 1990s.
	en.wikipedia.org /wiki/Exchange_bias (886 words)

	[Spintec - Spin electronics Research - France - Grenoble] (Site not responding. Last check: 2007-09-23)
		The dots are circular and show an enhancement of exchange bias with respect to the continuous films prepared under the same conditions.
		The dots are among the smallest reported in the literature but show a 40% decrease of exchange bias with respect to the continuous bilayer.
		Nevertheless, it is also observed that the exchange bias in AFM/FM nanostructures vanishes during heating at a temperature lower than that in which it vanishes in the continuous films with the same composition.
	www.spintec-lab.com /Exchange-bias.html (520 words)

	"GP31C-0099" in fm06
		We argue that this perpendicular arrangement of spins cannot yield exchange bias without some local rearrangement of spins close to the ilmenite-hematite interface.
		The results indicate that there is a threshold value of the hematite anisotropy constant below which the hematite spins become tilted out of the basal plane in the vicinity of the interface due to exchange interaction with the highly anisotropic ilmenite spins, thus creating a significant component of magnetisation parallel to c.
		Exchange bias is observed whenever there is a significant c component of magnetisation in the hematite phase.
	www.agu.org /cgi-bin/wais?hh=GP31C-0099 (513 words)

	Europhysics Letters (EPL)
		Positive exchange bias is shown to occur in (ferromagnetic (FeSn)/ferrimagnetic (FeGd)) bilayers.
		As the net magnetisation in the ferrimagnetic layer is not zero, in contrast to "regular'' exchange bias observed in ferro/antiferromagnetic systems, we could detect the magnetic configuration of both layers by magnetisation, ac-susceptibility and resistivity measurements.
		The results allow us to conclude that the exchange bias effect is due to an antiferromagnetic coupling at the interface between the magnetisation of the layers through a domain wall located at the interface.
	www.edpsciences.org /articles/epl/abs/2000/23/6328/6328.html (136 words)

	Theory of exchange bias (Site not responding. Last check: 2007-09-23)
		The exchange coupling of ferromagnetic and antiferromagnetic films across their common interface causes a shift in the hysteresis loop of the ferromagnet, called exchange bias.
		Variations, characteristic of the unidirectional anisotropy that gives rise to the loop shift, are observed in FMR experiments on exchange biased films, but are superimposed on an isotropic negative shift in the resonance field.
		Temperature Dependence of Exchange Bias in Polycrystalline Ferromagnet-Antiferromagnet Bilayers
	physics.nist.gov /Divisions/Div841/Gp3/Projects/Theory/theory_exbias.html (775 words)

	Researchers pin down phenomenon of 'pinning' of magnetic layers
		The phenomenon is known as exchange bias, or pinning.
		"The exchange bias phenomenon has been known for more than 45 years, but even though we have used the effect and even built sophisticated devices by trial and error, we haven't understood how it works," says Frithjof Nolting, an ALS researcher visiting from Stanford University.
		Because exchange-bias devices such as read heads depend upon an overall preferred magnetic orientation in a ferromagnetic layer, which is achieved by its coupling to the antiferromagnet, a "bias" is set during the manufacturing process.
	www.eurekalert.org /pub_releases/2000-06/LBNL-Rpdp-1306100.php (751 words)

	Department of Physics - Loyola University New Orleans
		The exchange bias is due to exchange coupling of interfacial spins of two magnetic materials from which one is antiferromagnetic and the other is either ferromagnetic or ferrimagnetic.
		The exchange biased structures have asymmetric or shifted hysteresis loops with respect to zero field.
		In spite of about 50 years long research on the exchange bias phenomenon there is no commonly accepted description of this effect.
	www.loyno.edu /physics/seminar/malkinski20041202.html (146 words)

	Depth Profile of Uncompensated Spins in an Exchange-Bias System
		The phenomenon known as exchange bias at the interface between a ferromagnet and an antiferromagnet is currently a subject of intense research because of its applications in the magnetic recording and read-head industries.
		Interactions across the interface between a ferromagnet and an antiferromagnet result in “exchange bias,” which locks the ferromagnet spins, thereby forming a reference layer with a fixed direction of magnetization that is one key to modern magnetic devices.
		In modern nanolayer magnetic devices, the shifted hysteresis loop centered on a nonzero magnetic field that characterizes exchange bias makes the ferromagnet an excellent magnetic reference layer because it is difficult to reverse the magnetization.
	www-als.lbl.gov /als/science/sci_archive/106exchange_bias.html (1039 words)

	OSU Physics: Calendar of Events
		The AF spin structure is the key to the understanding of exchange bias in FM/AF systems.
		The last topic is the oscillatory exchange bias in exchange-coupled itinerant AF, Cr.
		Using epitaxial (100)Cr/Py bilayer, we discovered for the first time an oscillatory exchange bias with temperature and pronounced effect due to the spin flip transition in Cr.
	www.physics.ohio-state.edu /calendar/event.php3?id=548 (247 words)

	OPUS3 - Magnetisierungsumkehr und -dynamik in Exchange-Bias-Systemen
		Exchange bias (EB) is a unidirectional anisotropy originating from coupling of a ferromagnetic with an antiferromagnetic layer.
		The exchange bias turns out to be the cause for the observed asymmetries.
		In the second part of this thesis, time-resolved measurements of exchange bias systems show a precession of the magnetization around the effective field after the pump pulse has changed the anisotropies of the sample by means of a local heating.
	darwin.bth.rwth-aachen.de /opus/volltexte/2006/1352 (598 words)

	Exchange bias using a spin glass (Site not responding. Last check: 2007-09-23)
		Exchange bias is commonly manifested as the hysteresis-loop shift observed when a ferromagnet is in contact with an antiferromagnet.
		Here, we report observations of exchange bias with unusual features of a ferromagnet in contact with a spin glass, demonstrating that this is a phenomenon of greater generality.
		The easily measured properties of the ferromagnet allow access to the internal magnetic degrees of freedom of the glass to which they are coupled.
	www.nature.com /nmat/journal/vaop/ncurrent/abs/nmat1809.html (179 words)

	Dr
		Exchange bias refers to the shift of magnetic hysteresis loop of a ferromagnet (FM) after being coupled to an antiferromagnet (AFM), due to the unidirectional anisotropy developed in the field cooling process.
		Along with the shift of the hysteresis loop is the enhancement of the coercivity due to the interfacial exchange coupling.
		The origin of the exchange bias effect is still hotly debated after almost fifty years of research, due to the difficulty in determining the magnetic interfacial structure as mentioned above.
	www.phys-astro.sonoma.edu /people/faculty/shi/research/index.htm (600 words)

	Graphics Gallery (Site not responding. Last check: 2007-09-23)
		The origin of exchange bias in our model is the antiferromagnetic exchange energy stored in AF domain walls when the external field reverses the ferromagnet.
		The AF exchange energy rises considerably and leads to asymmetric remanent states and thus to exchange bias.
		So, exchange bias results from the combination of switching and non-switching AF grains or the difference of the AF domain configuration between the positive and the negative remanent state.
	magnet.atp.tuwien.ac.at /gallery/exchbias/origin.html (255 words)

	Researchers Examining Phenomenon of Antiferromagnetism Underlying Computer Read Heads
		Because exchange-bias devices such as read heads depend upon an overall preferred magnetic orientation in a ferromagnetic layer coupled to an antiferromagnet layer, a "bias" is set during the manufacturing process.
		Apparently exchange bias is an intrinsic property of the interface, caused by the common alignment of the magnetic structure of both materials, even though initially there may be no total bias, averaged over a large area."
		Says Nolting, "This opens the door to new investigations, which may affect the way devices based on the exchange bias effect are manufactured" -- as well as the materials chosen to make them.
	www.lbl.gov /LBL-Science-Articles/Archive/antiferromagnetism-surprise.html (1018 words)

	Exchange bias in nanostructured materials (Site not responding. Last check: 2007-09-23)
		In the exchange bias phenomenon in antiferromagnet/ferromagnet (AF/FM) bilayers, one characteristic length scale is the size of the magnetic domains in both FM and AF (~1
		It is also technologically important as the exchange bias in AF/FM nanostructures provides an additional, tunable source of anisotropy to stabilize the magnetization, therefore possibly reducing the length scale that determines the superparamagnetic limit in magnetic recording.
		AMR measurements further confirm that the asymmetry is due to a coherent magnetization rotation process that exists primarily in the increasing-field branch of the hysteresis loop.
	ischuller.ucsd.edu /Nanoexbias.html (402 words)

	Free Exchange on Campus - Hey look, another study
		It would take some real investigating to find out how a professor presents his or her material, what the students learn, and other questions which are actually relevant in determining any sort of a "liberal bias" which shuts down other views and opinions.
		It needs to be said that this study and similar ones (such as the one cited from 2005 by Klein and Stern), are quite obviously right-wing attacks on higher education.
		While the authors may find that some personal beliefs of professors are left-leaning, they take that to mean that liberal professors are indoctrinating their students and denying the imaginary horde of would-be conservative professors access to any position among college faculty.
	www.freeexchangeoncampus.org /index.php?option=com_content&task=view&id=335 (476 words)

	Dissertation - Ph.D. Thesis Thomas Gredig 2002
		A large number of exchange bias induced properties are probed with various methods in the standard system of Co/CoO.
		Furthermore, exchange bias samples with non-mangetic spacer layers, such as Co/Ag/CoO trilayers were investigated.
		Its temperature dependence was correlated to the exchange bias effect.
	www.physics.ucsd.edu /~tgredig/thesis (322 words)

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