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Topic: Coercivity

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	AIM - The global trade assocation for automatic identification
		The trend is to move towards higher coercivity with values of 2100, 2750, 3600 and 4000 Oersteds being common.
		High coercivity magnetic stripes bring a new collection of parameters to the magnetic stripe world and higher is not always better.
		Coercivity is NOT a measure of signal amplitude.
	www.aimglobal.org /technologies/card/magnetic_stripe_faqs.asp (3209 words)

	Permanent Magnets
		The desirable properties of such magnets are typically stated in terms of the remanence and coercivity of the magnet materials.
		Both the coercivity and remanence are quoted in Tesla, the basic unit for magnetic field B.
		The materials with high remanence and high coercivity from which permanent magnets are made are sometimes said to be "magnetically hard" to contrast them with the "magnetically soft" materials from which transformer cores and coils for electronics are made.
	hyperphysics.phy-astr.gsu.edu /hbase/solids/magperm.html (571 words)

	United States Patent Application: 0030231077
		Thus, the threshold is set by choosing or adjusting the coercivity of at least one of the low-coercivity layers in the GMR films of the transpinnor.
		As described above, the low coercivity layers in the "off" switch do not function, i.e., the output current is zero irrespective of which of the two logic levels is asserted at the input, while those in the "on" switch do, i.e., the output signal corresponds to the input signal.
		However, when the high coercivity layers of the appropriate films in both switches are magnetized in the other direction, the roles of the low coercivity layers in the two switches are reversed.
	appft1.uspto.gov /netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=/netahtml/PTO/search-bool.html&r=3&f=G&l=50&co1=AND&d=PG01&s1=wuori&OS=wuori&RS=wuori (15134 words)

	Introduction to Magnetic Stripe
		Measured in Oersteds, coercivity is the measure of how difficult it is to encode information on the magnetic stripe.
		A standard bank card has a coercivity of approximately 300 Oe (Oersteds) and is considered to be low coercivity.
		The advantage of high coercivity is that it is harder to encode the information on the stripe.
	www.hightechaid.com /tech/card/intro_ms.htm (4427 words)

	ICMA - Industry Information
		This original encoding process produces a remarkable increase of coercivity, which is beyond the rewrite capability of a standard magnetic recording head.
		The new magnetic pigment is an inter-metallic compound compromised of particles composed of manganese and bismuth unrelated to the gamma-ferric iron oxide used in low coercivity (LoCo) or barium ferrite used in high coercivity (HiCo) magstripes.
		This once-encoded coercivity is so high that the encoded data can not be rewritten for the data densities involved in magnetic technology.
	www.icma.com /info/magadvance111200.htm (876 words)

	Hysteretic Property Measurements
		The flux density is measured using a coil wound on the yoke.
		Parameters such as coercivity, remanence, and hysteresis loss are estimated from the B-H curve.
		The small variation of coercivity around the metal-loss defect in the first figure is a result of measurement and instrumentation error and does not indicate a variation of the coercivity of the material.
	www.battelle.org /pipetechnology/DOTReport/links_direct/Hysteretic_Property.htm (484 words)

	[No title]
		Most notably, a substantial decrease in coercivity observed in several cases was correlated to a mixture of fcc and bcc crystalline faces in the film.
		Detailed microstructural and X-ray analysis revealed that the coercivity minimum was associated with the coexistence of fcc and bcc phases; effects such as grain size contributed to the strong compositional dependence of the coercivity.
		Measurements performed at low frequency using a disk with high coercivity (3800 Oe) showed that overwrite with the ternary alloy is clearly superior, demonstrating the advantage in using high- moment materials to improve recording performance.
	www.research.ibm.com /journal/rd/425/robertson.txt (5061 words)

	Chp. 5: Nanostructured Magnetic Materials
		We have shown that the highest coercivities are obtained in passivated particles that have a core/shell morphology with a metallic core surrounded by a (Fe /Fe (or berthollide) oxide shell consisting of small grains.
		The coercivity of the samples was found to decrease with the amount of soft phase, but the reduced remanence increased with values greater than 0.7.
		The studies on Fe-O films were designed to clarify whether the large increase of the coercivity and its observed anomalous temperature behavior in small passivated Fe (Co) particles are due to the presence of a particular oxide or are generic to all types of oxides.
	www.wtec.org /loyola/nano/us_r_n_d/05_04.htm (2039 words)

	Glossary (Site not responding. Last check: 2007-10-20)
		Coercivity, measured in Oersteds (Oe.), is very loosely defined as the magnetic field required to encode or erase a magnetic stripe.
		Ordinary low coercivity magnetic stripes (often called loco) are rated at 300 Oersteds; some others are in the range of 600-650 Oe.
		High coercivity stripes (often called hico or high energy) are generally in the range of 1250-4000 Oe.
	www.q-card.com /glossary.htm (3095 words)

	Videomaker Magazine Fishing for Blank Tape: Videotape Buyer’s Guide (Site not responding. Last check: 2007-10-20)
		Coercivity, measured in Oesteds (Oe), denotes the magnetic strength of a tape.
		Although compact VHS tape usually carries comparable coercivity and retentivity readings to VHS tapes, the main difference between VHS-C and its full-size family member is the smaller cassette.
		It has a coercivity of 1510 Oe and a retentivity of 4500 G. Sony's DVM60EXM has a 1500 Oe coercivity and a 5300 G retentivity, while the DVM60PR has a 1320 Oe coercivity and a 5000 G retentivity.
	www.videomaker.com /scripts/article.cfm?id=7288 (1810 words)

	Finger-Printing Exchange Bias (Site not responding. Last check: 2007-10-20)
		However, there is a small tail in the FORC diagram due to regions in the sample with higher coercivity.
		After an exchange bias is established, at 50 K, the FORC diagram shows a distribution of coercivity and exchange field that are consistent with the major-loop values.
		Surprisingly, the tail of higher coercivity regions bends towards lower exchange fields, contrary to the belief that the exchange field measured in a major loop is the lower limit of the exchange field across the sample.
	www.nsti.org /Nanotech2003/showabstract.html?absno=643 (257 words)

	Magnetic materials: from the search of new phases to nanoscale engineering
		Materials used for information storage have medium coercivity: the magnetisation-saturated states must be stable enough for the information not to be lost; at the same time, the writing process must be realised in a not oo high magnetic field.
		Such coercive field values can be obtained in materials, which show shape anisotropy: the moments tend to align along the long dimension of elongated particles.
		In (b), exchange coupling between soft and hard grains is at the origin of the global coercivity obtained In (c), exchange decoupling between grains is characteristic of materials for magnetic recording so that the magnetisation of any given region may be reversed,without influencing others.
	www.europhysicsnews.com /full/24/article6/article6.html (2660 words)

	Influence of Nanoporosity and Roughness on Thickness-Dependent Coercivity of Iron Nanonetwork (Site not responding. Last check: 2007-10-20)
		We have studied the coercivity of iron nanonetworks as a function of thickness, nominal pore diameter, and surface/interface roughness.
		For the the thickness range (2- 45nm) studied the film coercivity should have been independent of thickness for a film on ideal smooth substrate since Néel-type domain-walls will be energetically favourable in these thickness range.
		Based on the pore fill-up geometry, we have proposed a model for thickness-dependence of coercivity taking in to account of the effective porosity, critical thickness at which the pore will be completely filled up.
	www.ul.ie /~cost523/magnetic/Tofail.htm (343 words)

	Tape Articles Part 3 by Bill Vermillion
		The first - coercivity - is how much energy we have to use to force a change in the magnetic state.
		A low coercivity material is known as being soft magnetically, while a high coercivity is considered to be hard.
		We have to use a higher coercivity to as not to erase the adjacent particle and we also have to have a higher retentivity - more remaining magnetism - because the particles are now smaller and have to do more work.
	aplawrence.com /BillV/part3.html (2693 words)

	About Degaussing (Erasing) Magnetic Media - Tape, Tape Cartridges, Video and Audio Tape, Hard Drives, Zip Disks
		Simply stated, coercivity is the magnetic field strength, rated in oersteds (Oe), required to change the magnetic orientation of the magnetic material.
		Examples of typical coercivities for computer magnetic tapes and disks are shown in table I. Data is typically not lost until its level has been decreased 65% to 75% (or more) below its original saturation recording signal level, dependent upon the drive system.
		For higher coercivity media, four passes are often recommended — two passes, with a 90 degree rotation for the second pass, and then repeat the process with the media turned upside-down.
	www.periphman.com /degaussing/tape-degaussing/degaussing-erasing.shtml (486 words)

	Office Zone - Magnetic Reader / Encoder FAQS
		LOW COERCIVITY: As the name implies, low field energy is used to write data onto the magnetic stripe of an ID card designed for low-energy encoding.
		HIGH COERCIVITY: High-coercivity uses strong magnetic field energy to write data onto the magnetic stripe of an ID card designed for high-energy encoding.
		It is important to use the appropriate encoder-type printer with the appropriate coercivity cards.
	www.xmission.com /~ozone/ozone/read_faq.htm (513 words)

	PVC Mag Stripe
		Coercivity is the term used to designate how strong a magnetic field must be to affect data encoded on the stripe, and therefore, how immune the data is to damage.
		Measured in Oersteds (Oe), the coercivity of a common credit card is about 300 Oe, considered low coercivity.
		High coercivity (HiCo) magnetic stripe technology relies on particles -- generally barium ferrite (low coercivity uses iron oxide) -- with coercivity values ranging from 2500 to 4000 Oe.
	www.smartcardsupply.com /Content/Cards/magstripe.htm (236 words)

	Evolution of strength and coercivity during annealing of FeCo based alloy
		There is confusion in the literature about the cause of an observed discontinuity in the variation of strength and coercivity as a function of the temperature at which cold-rolled Fe-Co alloys are annealed.
		In the present work, published data for grain growth, coercivity and strength are used to solve the apparent inconsistencies.
		Using published data on magnetic and mechanical properties of FeCo based alloys, it has been possible to show that the coercivity and the strength of FeCo-2V as a function of annealing treatment can be fully understood in terms of the fully recrystallised grain size.
	www.msm.cam.ac.uk /phase-trans/2004/FeCo (1372 words)

	Magnetic marker for locating a splice within magnetic tape - Patent 4325087
		This coercivity is of an adequately high magnitude to resist the unintentional erasure of a prerecorded magnetic pattern on the marker as the magnetic tape undergoes coventional magnetic recording and playback operations.
		The prerecorded magnetic pattern on the high coercivity marker can however be detected and used to signal the location of the splice, and thus the location of the message.
		In both embodiments of the marker 10 or 40 described above, the magnetic layer has a coercivity of approximately 3500 oersteds and a retentivity of approximately 0.1 line of flux and can be recorded with a magnetic pattern by using a magnetic recording head capable of producing an adequately high field strength.
	www.freepatentsonline.com /4325087.html (1997 words)

	What's With this Magnetic Stripe Stuff
		It suggests that a high coercivity stripe is harder to duplicate or counterfeit and unfortunately this is not true.
		The ISO committee is now working on a similar set of standards for high coercivity cards, but the document is only in a working form at the moment and is not likely to be released for Draft Review until next year at the earliest.
		The next move, especially if your primary interest is in high coercivity is to get the AIM Guideline for Measurement of Effective Magnetic Parameters of Magnetic Stripes on Media.
	www.hightechaid.com /tech/card/what_ms.htm (2730 words)

	Glossary of terms (Site not responding. Last check: 2007-10-20)
		Coercivity is a measure of the magnetic field that is needed to reduce magnetization in a thin-film layer to zero.
		The measure for coercivity is an Oersted (Oe).
		CPU is on a single chip that performs arithmetic and logical operations, decodes and executes instructions.
	www.usbyte.com /common/glossary_C.htm (410 words)

	[No title] (Site not responding. Last check: 2007-10-20)
		This resulted in the destruction of all media with a coercivity greater than 750 oersteds and most magnetic disks when they were no longer needed in support of the classified mission.
		Type I magnetic tape has a coercivity factor (amount of electrical force required to reduce the recorded magnetic strength to zero) not exceeding 350 oersteds (unit measure of the magnetizing force to produce a desired magnetic strength across a surface) and can be used to sanitize (degauss) all Type I media.
		Type II magnetic tape has a coercivity factor between 350 and 750 oersteds and can be used to sanitize all Type I and II media.
	www.dss.mil /infoas/magnetic_tape_degaussing.doc (733 words)

	5800 HMM
		The 5800 Hard Metal Magnetometer (HMM) from Walker LDJ Scientific is a new instrument designed to measure both the magnetic saturation and coercivity of cemented carbides.
		Magnetic saturation and coercivity of the sample are acquired and displayed on the PC Monitor.
		These lower fields do not guarantee that the sample is magnetically saturated in all orientations, and lead to sample geometry and orientation effects on both magnetic saturation and coercivity measurements.
	www.walkerldjscientific.com /Products/Product_Lines/Magnetic_Analysis/5800_HMM/5800_hmm.html (678 words)

	Coercivity (Site not responding. Last check: 2007-10-20)
		The level of demagnetizing force that would need to be applied to a tape or
		A demagnetizing field of a level in excess of the coercivity must be applied to a magnetic particle in order to coerce it to change the direction of its magnetization.
		Coercivity is the property of a tape that indicates its resistance to demagnetization and determines the maximum signal frequency that can be recorded by a tape.
	www.screensound.gov.au /glossary.nsf/Pages/Coercivity?OpenDocument (87 words)

	78(R) SB 1673 - Introduced version - Bill Text (Site not responding. Last check: 2007-10-20)
		Coercivity of magnetic media defines the magnetic field necessary to reduce a magnetically saturated material's magnetization to zero.
		The level of magnetic media coercivity must be ascertained before executing any degaussing procedure.
		It is essential to determine the appropriate rate of coercivity for degaussing; (2) shielding materials (cabinets, mounting brackets), which may interfere with the degausser's magnetic field, must be removed from the hard drive before degaussing; and (3) hard disk platters must be in a horizontal direction during the degaussing process.
	www.capitol.state.tx.us /tlo/78R/billtext/SB01673I.HTM (1461 words)

	Section 2B
		The most recent rare earth powder to be introduced is samarium-iron-nitride, which was the result of a search for alternatives to the very popular neodymium-iron-boron, but which unfortunately uses a rare earth element which is considerably less plentiful.
		The resulting intrinsic coercivity is roughly inversely proportional to the grain size.
		composition causes a reduction in intrinsic coercivity, it is generally easier to magnetize a nanocomposite magnet.
	www.magnetweb.com /Sect2B.htm (886 words)

	Size-control and size-selection at the nanosize level: Production of CoFe2O4 nanoparticles of unusual high coercivity ...
		The cobalt ferrite particles of 40 nm exhibited hither to reported coercivity value of 4.65 kOe, which was close to the theoretical value of 5.3 kOe, a moderate magnetization of 50 emu/gm and squareness ratio of 0.66 at room temperature.
		An advantage of seeding method is the ability to produce large amounts of ferrite in an economical and viable way for magnetic recording applications.
		The synthesis technique, which was key to the success of producing highly crystalline cobalt ferrite with unusually high coercivity, could be extended to the synthesis of ceramic and semiconductor single domain particles of nanometer size with properties close to the theoretical predictions.
	www.nsti.org /Nanotech2003/showabstract.html?absno=622 (225 words)

	Epitaxial Strontium Hexaferrite (SRM) films have been grown on (100) oriented LaAIO3 substrates by laser ablation at ... (Site not responding. Last check: 2007-10-20)
		Room temperature magnetization measurements of both films have been completed using a Princeton Instruments Corp. alternating gradient magnetometer, with the magnetic field applied parallel and perpendicular to the surface of the substrate.
		The coercive force is large in both orientations, so that saturation is not obtained in the available magnetic field.
		Room temperature magnetisation of Film "B", with the magnetic field applied parallel and perpendicular to the surface of the substrate.
	ablation.magnet.fsu.edu /papers/strhex.htm (860 words)

	Experimental Results
		The direction of the shift depends on the orientation of the NiFe layer magnetization during field cooling.
		In addition to the loop shift, the interfacial interaction increases the coercivity dramatically.
		Perpendicular to the loop shift direction, the hard axis loop (not shown) passes nearly linearly through zero with almost no coercivity.
	www.wsrcc.com /alison/newnio/results.html (861 words)

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