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Topic: Magnetic domain

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	Hollow magnetic domain recording device - Patent 4004287
		Domains are to be understood to mean those regions in which the direction of the magnetization is directed opposite to the external magnetic field.
		A known method of causing domains to move is based on the presence of conductive tracks suitable for that purpose along which the domain moves in a desirable direction on the basis of periodic changes in the size of the domain (caused by a periodically varying magnetic field).
		Also with a structure of a hollow domain with a single-walled domain present within it, a variation in the domain sizes which is non-reversible and quite different from that of a single-walled domain occurs as a function of the external field H.sub.o in the presence of a given coercive force.
	www.freepatentsonline.com /4004287.html (2659 words)

	Apparatus and method of forming a magnetic domain strain gage - Patent 4979395
		The magnetic domain strain gage 20 includes an electrically conductive element 22, which may be for example, a wire or a ribbon of ferromagnetic material and is preferably a ribbon of amorphous metal.
		For application in magnetic domain strain gages, the greatest linearity is presumed to be achieved by selection of materials in which the magnetoelastic contribution to the total anisotropy energy dominates the contributions from the magnetocrystalline and field-induced anisotropy energies.
		In the case of an amorphous iron-based alloy the hysteresis loop is characterized as having a steep slope at the intersection of the H axis.
	www.freepatentsonline.com /4979395.html (6166 words)

	Weiss domains - Wikipedia, the free encyclopedia
		Weiss domains are small areas in a crystal structure of a ferromagnetic material with uniformly oriented magnetic momenta.
		By nature the Weiss domains are magnetized to the full saturation.
		Weiss domains are also found in ferroelectric materials and form areas of uniform dipole orientation there.
	en.wikipedia.org /wiki/Magnetic_domain (142 words)

	Disorder-Induced Microscopic Magnetic Memory
		The coherent magnetic speckle metrology technique at ALS Beamline 9.0.1 was used to directly probe the effect of disorder on the spatial structure of the magnetic domain configuration.
		To be sensitive to the magnetic domains, the photon energy was tuned to the cobalt 2p→3d resonant transition.
		Starting from positive saturation (all the magnetic spins are pointed up), small areas of the sample begin to reverse their magnetization, then a labyrinth of magnetic domains is produced, and finally the remaining up domains grow smaller and eventually disappear completely when the spins are uniformly pointed down.
	www-als.lbl.gov /als/science/sci_archive/109magmemory.html (1003 words)

	audiblemagneticdomains (Site not responding. Last check: 2007-10-30)
		When you bring a magnet toward a piece of iron, the domains which are aligned in the same direction as your magnet grow larger at the expense of their neighboring domains.
		The sudden motion of the domain walls in the iron produce pulses of electric current in the coil which are turned into sound by the amplifier and speaker.
		Magnetic Domains were discovered by Weiss in 1926.
	www.exo.net /~pauld/activities/magnetism/audiblemagneticdomains.html (421 words)

	Domain - Wikipedia, the free encyclopedia
		domain (physics), a region of a solid inside which a property is uniform (for example magnetic domain in ferromagnetism)
		a software engineering domain - a field of study that defines a set of common requirements, terminology, and functionality for any software program constructed to solve a problem in that field.
		In Database Theory, a data domain is a set of all permitted atomic values.
	en.wikipedia.org /wiki/Domain (399 words)

	MAGNETIC DOMAINS (Site not responding. Last check: 2007-10-30)
		The device uses polarized light to view the magnetization of domains in a ferromagnetic garnet, which has the property of rotating the plane of polarization of the light by an angle dependent on its magnetization.
		Magnetic domain structure in the garnet is viewed as shown in the photograph.
		If the magnetic field in which the sample is positioned is increased the domain alignment becomes more complete, and the lines vanish, sometimes leaving a "magnetic bubble," a single small group of domains aligned opposite the surrounding area.
	www.physics.brown.edu /physics/demopages/Demo/em/demo/5g2020.htm (206 words)

	MIT Magnetic Materials Group
		Magnetic domains form to reduce the magnetostatic energy associated with a surface across which these exists a discontinuity in the normal component of magnetization.
		The phase diagram suggests that the magnetization pattern in the 7 nm film is the result of a fully perpendicular magnetization vector.
		The magnetization in these closure domains is not parallel to the surface (as would usually be the case) but is canted out of the film plane due to the surface anisotropy (van Schendel and Hug).
	web.mit.edu /bobohand/www/domain.html (620 words)

	Texas Materials Institute \| magnetic materials (Site not responding. Last check: 2007-10-30)
		Magnetic thin films including multilayer stacks are being used in a broad range of sensor and information storage applications including GMR-based read/write heads and random access memories, and in spin-polarized electron injection devices.
		Microstructures and nanostructures of magnetic materials fabricated by STM chemical vapor deposition, and contact mask lithography techniques are being used to explore magnetotransport in quantum wires, and domain dynamics in micron scale structures.
		The magnetic materials and the magnetic structures, including multilayer stacks, microstructured and nanostructured materials that are being studied in the TMI, have broad applications in magnetic sensor technology (GMR read-write head, magneto-optic storage) and in device structures (MRAM, spin-injection transistors) that are being developed for microelectronics and communication technology.
	www.tmi.utexas.edu /research_area_magnetic.shtml (537 words)

	Hard disk - Wikipedia, the free encyclopedia
		The magnetic medium (film) on the disk surface changes its magnetization in microscopic spots due to the head's write field, which is a strong and highly localised magnetic field.
		The magnetic surface in the hard drive is divided into small sub-micrometre-sized magnetic regions, each of which is used to represent a single binary unit of information.
		All of the grains in a magnetic region are expected to point in the same direction, so that the magnetic region as a whole also has a magnetic dipole moment and an associated magnetic field.
	en.wikipedia.org /wiki/Hard_disk (6540 words)

	Witold Szmaja Home Page (Images of domain structures) (Site not responding. Last check: 2007-10-30)
		In the absence of external magnetic field, fine magnetic particles are preferentially attracted to the regions near domain walls, while in sufficiently large external fields (usually some tens or hundreds of oersteds), they deposit more favourably on the domains with the same orientation of magnetization as the external field.
		The type-I magnetic contrast is observed under the proper geometry between the specimen and the detector, as the stray fields of opposite directions deflect the secondary electrons in two opposite directions, either towards or away from the detector.
		SEM type-I magnetic contrast image of the domain structure in a 35 micrometers thick cobalt monocrystal (a) and comparison of the observed type-I magnetic contrast signal (squares) with that predicted theoretically (solid curve) (b) [W. maja, J. Magn.
	www.fic.uni.lodz.pl /kfcs/Mat_Lab/exdsws.htm (1334 words)

	Publications from the Magnetic Materials Group at NIST
		The domain size was observed to increase with the thickness of the Co layer.
		Magnetic measurements show that these materials are ferromagnetic at room temperature and remain so (with decreasing saturation magnetization) up to near the Curie Point of alpha-Fe, 770 °C. However, near 600 °C on heating (and also near 400 °C on cooling) the magnetic susceptibility indicates the existence of a magnetic phase change.
		The thermal hysteresis observed in the magnetic and thermal data is due to the sluggishness of the latter transformation.
	www.metallurgy.nist.gov /magnet/publications/maggrp.abstracts.html (4279 words)

	Cornell News: magnetic domain switching
		Schematic representation of a sandwich of cobalt and copper layers on a silicon substrate used to demonstrate the switching of magnetic domains by use of an electric current.
		By passing an electrical current perpendicularly through the layers, the researchers were able to reverse the orientation of the magnetic moments in a region of the thinner cobalt layer, while leaving the thicker layer unchanged.
		The orientation of the magnetization in the two layers can be read by simply passing a much weaker electric current through the two layers, because the resistance is much higher when the two moments are non-parallel.
	www.news.cornell.edu /releases/Aug99/magnetic_memory.ws.html (756 words)

	Session K16 - Magnetic Measurements.
		After magnetic saturation along the length of the bar, the remnant state consists of a large domain magnetized along the saturating field direction and a closure domain pattern at the end of the bar.
		As a magnetic field is applied opposite the original magnetizing field, parallel to the long axis of the bar, the closure domains grow at the expense of the main domain.
		By subtracting the linear components of the magnetization due to the response of the diamagnetic shells and the antiferromagnetic cores, we are left with a Langevin-like magnetization of the unblocked net moment.
	flux.aps.org /meetings/YR98/BAPSMAR98/abs/S2020.html (1695 words)

	Session L22 - Magnetic Nanostructures V: Magnetic Imaging and Domain Structure.
		We observe a "localization" of domain wall motion near the topological defects of the domain structure and an evolution of the excitation patterns with the external field.
		The magnetic structure as a function of the externally applied magnetic field was observed for the buried SmCo layer of the material using magnetic dichroism contrast at the Sm L-III edge (6.716 keV).
		We succeeded to clearly observe the magnetic vortex core in permalloy (Ni80Fe20) circular dots with diameter from 0.1 to 1 micrometer by using magnetic force microscopy (MFM).1 MFM observation for permalloy circular dots was carried out after applying various magnetic fields and the annihilation field of the magnetic vortex core was estimated.
	flux.aps.org /meetings/YR01/MAR01/abs/S4320.html (1841 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)

	TEL-Atomic - Magnetic Bubble Apparatus
		In the search for magnetic materials which could be used for bubble memories, Bobeck discovered that ferrimagnetic garnets (FMG) could be "engineered" to produce the very small, isolated cylindrical domains (called bubbles because of the end-on shape when viewed) which were stable yet capable of being formed, moved and destroyed at very high rates.
		Materials are magnetic because of the anisotrophy and this in turn means there is interaction between the electrons when any electromagnetic radiation passes through.
		In the unmagnetised state FMG contains equal volumes of both kinds of domains, and when an external magnetizing field H is applied, magnetization occurrs by the growth of one domain at the xpense of the others.
	www.telatomic.com /mba.html (500 words)

	Time and layer resolved magnetic domain imaging using PEEM
		Magnetization reversal dynamics at nanosecond timescales is an important subject for many technological applications of magnetic materials.
		Panels b–k show magnetic domain images of the FeNi layer in a FeNi/Al /Co spin-valve structure during the application of bipolar magnetic field pulses of 80 ns length (a).
		Micromagnetic simulations support the experimental observations and reveal that the locally enhanced nucleation is due to magnetic stray fields of the domain walls in the Co layer.
	www.physik.fu-berlin.de /~ag-kuch/TR_PEEM.html (530 words)

	Michael J. Donahue: Selected Abstracts
		Domain wall momentum and retrograde domain wall motion are both observed and explained by the analytical model.
		In the presence of an external magnetic field, the field gradients near the magnetic elements are sufficiently large to trap magnetic particles that are separated from the patterned films by a 200 nm thick nitride membrane.
		In this paper a new method is described that uses a "domain wall trap" element shape to reduce both the coercivity and the dependence of coercivity on element size in submicron magnetic elements.
	math.nist.gov /~MDonahue/pubs/abstracts.html (4293 words)

	Observation of Magnetic Domains
		Under the action of the gradient in the stray magnetic fields, the colloid particles are attracted to the regions of maximum magnetic field, which coincide with the lines at which the domain boundaries intersect the surface.
		The domain pattern shown is usually referred to as a “cog wheel” pattern and is observed when uniaxially anisotropic samples are sectioned perpendicular to their easy direction of magnetisation.
		The Kerr effect has been developed as an accurate method of characterising the magnetic properties of thin film samples that could not be measured by conventional methods due to the small volume of magnetic material present.
	www.aacg.bham.ac.uk /magnetic_materials/observation_domains.htm (515 words)

	Magnetic imaging by PEEM (Site not responding. Last check: 2007-10-30)
		The magnetization reversal of magnetic microstructures can be followed with the PEEM by applying short magnetic field pulses between the acquisition of domain images.
		Close to spin-reorientation transitions typical magnetic domain patterns, characterized by a branching into smaller and smaller stripe domains, are frequently observed.
		The magnetic coupling at the interface between an antiferromagnetic and a ferromagnetic layer is of highest fundamental and technological importance due to the phenomena encountered ("Exchange Bias").
	www.mpi-halle.de /~wme1/research/bessy/PEEM.htm (354 words)

	Nanopicture of the Day - Magnetic Domain Walls - May 25, 2004
		Magnetic force microscopy (MFM) was introduced in 1987 as a new technique for mapping the field distribution on a microscopic scale.
		The technique relies on the detection of magnetic forces or force gradients exerted on a probing tip while the tip is scanned over the sample surface.
		From the time of invention of MFM the performance of this technique was tested in applying it to different magnetic materials from hard magnets like FeNdB to soft ones like garnets.
	www.nanopicoftheday.org /2004Pics/May2004/MagDomWalls.htm (155 words)

	Magnetic Domain (Site not responding. Last check: 2007-10-30)
		A magnetic domain is region in which the magnetic fields of atoms are grouped together and aligned.
		In the experiment below, the magnetic domains are indicated by the arrows in the metal material.
		But, when the metal became magnetized, which is what happens when it is rubbed with a strong magnet, all like magnetic poles lined up and pointed in the same direction.
	www.ndt-ed.org /educationresources/HighSchool/Magnetism/magneticdomain.htm (245 words)

	Introduction
		A remanent magnetization is defined as the magnetization that exists in the absence of an external magnetic field.
		The foundations of theoretical rock magnetism were laid down in an elegant paper by Neel [1949] dealing with the theory of thermal remanent magnetization (TRM) in an ensemble of identical noninteracting single domain (SD) (uniformly magnetized) particles.
		The term pseudo-single domain (PSD) was first introduced by Stacey [1958] to describe the magnetic moment in a MD grain associated with the sudden (Barkhausen) jump of a domain wall as it becomes dislodged from a defect.
	www.agu.org /revgeophys/merril00/node1.html (869 words)

	Vural, Kadri L. (1980-05-05) Magnetic domain wall dynamics in the presence of an in-plane field. ...
		Vural, Kadri L. (1980-05-05) Magnetic domain wall dynamics in the presence of an in-plane field.
		The purpose of this work is to understand the domain wall dynamics in the presence of high drive fields and inplane fields in magnetic bubble materials.
		The domain wall is dynamically deformed through the thickness at high drive and in-plane fields.
	etd.caltech.edu /etd/available/etd-09212004-103313 (221 words)

	Caltech Press Release, 9/1/2004, Dr. Michael Roukes
		Now, scientists at the California Institute of Technology have developed a novel method of measuring the resistance of "domain walls," which are the nanoscale boundaries separating areas of a magnetized material that possess different magnetic alignments, or a "twist" of magnetic spins.
		During that time, they are able to carry out extremely sensitive electrical measurements to identify the tiny amounts of resistance generated by this trapped single magnetic domain wall.
		Understanding the dynamics of magnetic domain walls is crucial for magnetic storage devices such as magnetic hard drives, and for future magnetic memories.
	pr.caltech.edu /media/Press_Releases/PR12578.html (530 words)

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