DOCSLIB.ORG

615-0300 (20-030) and 615-0305 (20-035) Electromagnet Written by Dr

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
615-0300 (20-030) and 615-0305 (20-035) Electromagnet Written by Dr ©2012 - v 5/09 615-0300 (20-030) and 615-0305 (20-035) Electromagnet Written by Dr. P.G. Mattocks Introduction: Activities few inches above the surface. This compact electromagnet is able If conditions are right, sur- to lift 100 times its weight - up to 200 faces smooth, tray loaded and pounds (20-030) or 500 pounds (20- Demonstrate Holding Force 035), with only one or two 1 1/2 volt D A quick way to demonstrate holding hanging correctly, you can cell batteries as a power source! This is force is to connect batteries, place core carry over 200 pounds. due to precision machining of the flat and yoke together, and try to pull apart Reverse connections and confirm surfaces (core and yoke). Compare it to with your two hands. If your surfaces the same load can be carried. cranes that can lift derelict automobiles are flush and connections good, you Variations: Stand on a bathroom scale around a junk yard. These cranes use will not be able to separate the parts. underneath the magnet and pull electromagnets similar in principle to Now disconnect battery. Parts remove down on the yoke. (Take care the this one, although with higher power easily. yoke does not hit your head. Avoid requirements. This style of crane For a quantifiable demonstration, the in ropes!) The reading on scale is practical since it can be switched you will need: will decrease by amount of the force on and off remotely and loaded and • Weights between magnet and yoke. If you unloaded by one person. • Tray for holding weights weigh 240 pounds and the yoke Warranty and parts: • Safety strap separates at a reading of 40 pounds, We replace all defective or missing parts free • Connection to beam1. the maximum holding force is 200 of charge. Additional replacement parts may be pounds. If you weigh less than 200 ordered toll-free. We accept MasterCard, Visa, Hang magnet as shown in Figure 1.2. pounds, this little magnet should be checks and School P.O.s. All products warranted Add known weights to tray until able to bear your full weight. to be free from defect for 90 days. Does not ap- yoke falls off. ply to accident, misuse or normal wear and tear. Intended for children 13 years of age and up. The safety strap will catch the This item is not a toy. It may contain small parts yoke but not the tray, provided Dependence on Current that can be choking hazards. Adult supervision 1. Attach as in first demonstration is required. the tray was initially only a 2. Change the current as shown: For best results: • Do not scratch mating surfaces. batteries or heavy duty Keep mating surfaces clean, smooth beam power supply variable resistor and undamaged. If surfaces do not mate properly, poles appear which connection reduce strength. Smear grease or safety strap to beam oil between use or while storing. Remove before using. electromagnet • Do not operate near a watch, color coil TV or other electrical appliance. Core Figure 2: Connecting Battery & Resistor • Do not switch on current until magnet surfaces are aligned to prevent Yoke damage from sudden impact. 3. Place known weight on tray and vary • To calculate the force required current until it falls. to remove the yoke, compare the Graph load against current and note that weight pan energy contained in the magnetic load does not increase linearly with field with separation of the yoke. It current. This is because the iron is should agree with the 200 pounds well magnetized and approaching found experimentally. table top saturation. (See Theory in following sections.) Operation Requires: Warning: The coil will overheat in a one or two D cell batteries Figure 1: How to Hang Electromagnet few minutes with currents of 2 or more amps. 1 SCIENCE FIRST® | 86475 Gene Lasserre Blvd., Yulee, FL 32097 | 800-875-3214 | www.sciencefirst.com | [email protected] SCIENCE FIRST® | 86475 Gene Lasserre Blvd., Yulee, FL 32097 | 800-875-3214 | www.sciencefirst.com | [email protected] ©2012 - v 5/09 Dependence on Gap terminal will therefore be negative during cause them to be magnetic. 1. Repeat procedure above. induction and vice versa. These thermal properties are employed 2. Place one or more layers of alu- Because the induction is brief, the in magnetic heat engines. minum foil (about .005 inch, depending value obtained cannot be predicted be- Exploring magnetic field upon type of foil) between electromagnet cause it is too dependent on voltmeter around electromagnet and yoke. response-time. An ammeter can also be 1. Place sheet of cardboard (or Because aluminum is nonmagnetic used to detect the brief flow of current of other nonmagnetic material) over and no free poles appear at iron surface, a few milliamperes that results. upturned face of magnet. the effect of coil current on iron is re- 2. Sprinkle iron filings over the duced. Even one thousandth of an inch of Dependence on magnet face. foil will reduce the holding force to 100 Temperature(Curie Use a small hand-held compass to lbs. This confirms the need for smooth Temperature) identify poles. The North pole of the surfaces in an electromagnet. 1. Hold steel wire coat hanger close compass (that which seeks the Earth’s to electromagnet. Observe attraction. Replace iron yoke with other North Pole) will point to the South pole 2. Heat same short section of wire of the magnet (which seeks the South substances with propane torch. pole of the Earth). 1. In place of yoke try other materials Warning: Do not heat electromagnet! - copper, aluminum, brass etc. Confirm Observe that red-hot steel is no longer that these materials are nonmagnetic.2. Theory attracted but that on cooling magnetism Part One: Background Use core of magnet to lift other iron is restored. At high temperatures, objects in addition to yoke. Use iron Sailors have known of naturally oc- thermal agitation destroys alignment objects with flat surfaces free of rust and curring permanent magnets for thousands within each domain. paint (i.e: base of iron cooking pot; base of years. In the 1800’s, connections When a few spins are shaken out of carpenter’s wood plane). Try to attain between magnetism and electricity were of alignment, their influence is lost holding forces of 40 lbs. studied by Ampere, Maxwell, Biot-Sa- over neighboring spins which in turn vark, Curie etc. Together their equations Remanence are more easily shaken. The magnetic “solve” (accurately predict outcome of) character does not trail off over an ill- 1. Put yoke in place and connect coil given physical situations. But these were defined temperature range but drops to cell for a few seconds so domains are of a phenomenological nature. While at an increasing rate until it vanishes aligned as before. equations quantified the observed math- at a particular material-dependent 2. Disconnect coil. You will need to ematical relationships between electricity temperature (the or apply a few pounds of force to pull yoke Curie Temperature, and magnetism in the form of “laws”, ) For iron, Tc is 770 ° C; in contrast, off. Not all domain walls moved back Tc. they did not give insight into why there red heat becomes just barely visible in when cell was disconnected. Due to the should be two seemingly different but a dark room at about 700° C. There closed magnetic circuit, there are no free related effects as magnetism and elec- is no connection between these two poles even in iron to drive domain walls tricity. Both were seen to depend upon effects but red heat does make a useful back past the few pinning sites. electric charge. thermometer. 3. Pull yoke off to break magnetic Most people believed these inter- There are two other common circuit. Reapply yoke. You’ll see that lit- twined but apparently different effects magnetic materials. The found in tle force is required to pull it off again. flint had common explanations. Einstein’s cigarette lighters, an alloy of iron and Theory of Relativity (1905) provided the Demonstrate Induction curium, is magnetic with Tc of about missing connection. It stated that length, 100° C. Suspend a cigarette lighter on The remanence noted above time and mass transform according to cotton thread and observe as it pulls to the relative velocity between observer may be used to demonstrate the electromagnet. Dip in boiling water; and observed. Even though a stationary induction. the attraction disappears until the flint electric charge produces certain effects 1. When disconnecting coil from cell, cools. on its surroundings (described as an connect coil to DC voltmeter. Some brass screws are nickel-plated. electric field) the electric charge, when 2. Pull off yoke. Voltmeter will The nickel is ferromagnetic with Tc of moving, produces a different effect due briefly register aninduced voltage. 360° C. Despite thin plating, if you to those transformations. This effect is This is because magnetism in the iron is suspend the screw by a brass wire, what is described as the original electric collapsing as domain walls are driven back you’ll see attraction to the electromagnet. field due to static charge plus a magnetic by free poles. This, according to Lenz’s Gentle heating - take care not to melt field caused by the movement of the Law, induces a voltage in the coil in order wire! - will cause the nickel to become charge. In this case, the magnetic field is a to sustain the magnetism. It tries to replace nonmagnetic below red heat but above relativistic correction to the electric field. current that magnetized the iron in the first boiling water temperature.
Load more

Recommended publications
  • DMI Interaction and Domain Evolution in Magnetic Heterostructures with Perpendicular Magnetic Anisotropy
    Georgia State University ScholarWorks @ Georgia State University Physics and Astronomy Dissertations Department of Physics and Astronomy Spring 4-30-2018 DMI Interaction and Domain Evolution in Magnetic Heterostructures with Perpendicular Magnetic Anisotropy Jagodage Kasuni S. Nanayakkara Follow this and additional works at: https://scholarworks.gsu.edu/phy_astr_diss Recommended Citation Nanayakkara, Jagodage Kasuni S., "DMI Interaction and Domain Evolution in Magnetic Heterostructures with Perpendicular Magnetic Anisotropy." Dissertation, Georgia State University, 2018. https://scholarworks.gsu.edu/phy_astr_diss/102 This Dissertation is brought to you for free and open access by the Department of Physics and Astronomy at ScholarWorks @ Georgia State University. It has been accepted for inclusion in Physics and Astronomy Dissertations by an authorized administrator of ScholarWorks @ Georgia State University. For more information, please contact [email protected]. DMI INTERACTION AND DOMAIN EVOLUTION IN MAGNETIC HETEROSTRUCTURES WITH PERPENDICULAR MAGNETIC ANISOTROPY by JAGODAGE KASUNI NANAYAKKARA Under the Direction of Alexander Kozhanov, PhD ABSTRACT My thesis is dedicated to the study of the magnetic interactions and magnetization reversal dynamics in ferromagnetic heterostructures with perpendicular magnetic anisotropy (PMA). Two related projects will be included: 1) investigating interfacial Dzyaloshinskii-Moriya interaction (DMI) in multilayer structures; 2) controlled stripe domain growth in PMA heterostructures. Magneto Optic Kerr Effect microscopy and magnetometry techniques along with vibrating sample magnetometry were used to investigate these phenomena. The CoPt bi-layer system is a well-known PMA material system exhibiting DMI. However, films with many CoPt bi-layers are known as having zero effective DMI due to its inversion symmetry. I focused my research on CoNiPt tri-layer heterostructures with broken inversion symmetry.
    [Show full text]
  • Successful Observation of Magnetic Domains at 500℃ with Spin
    FOR IMMEDIATE RELEASE Successful observation of magnetic domains at 500℃ with spin-polarized scanning electron microscopy Contributing to magnetic material development and performance improvement of devices such as HDD Tokyo, September 21, 2010 --- Hitachi, Ltd. (NYSE : HIT/TSE : 6501, hereafter Hitachi) today announced the development of Spin-polarized Scanning Electron Microscopy (hereafter, spin-SEM) technology for observation of magnetic domains under high temperature conditions in a magnetic field. Using this technology, changes in the magnetic domain structure of a cobalt (Co) single crystal was visualized up to 500 degrees Celsius (C). By applying the technology developed, the temperature conditions for observing magnetic domains in a sample can be heated up to 500C when using only the heating unit, and up to 250C when used in combination with a function to apply a magnetic field of up to 1,000 Oersteds (Oe). As a result, it is now possible to fully utilize the spin-SEM feature of high-resolution magnetic domain observation while observing the effect of temperature and external magnetic field on magnetic materials. It is expected that in the future, this technology will contribute to the development of new materials for permanent magnets and performance improvements in magnetic devices such as hard disk drives (HDD), etc. Spin-SEM is scanning electron microscopy which focuses a squeezed electron beam on a sample surface and measures the spin (the smallest unit describing magnetic property) of the secondary electrons emitted from the sample to observe the magnetic domain (the region where the spin direction is the same). It has a high resolution (10nm for Hitachi instrument) compared with other magnetic domain observation instruments and can be used to analyze magnetization vector.
    [Show full text]
  • Magnetic Forces ©Lluís Real/Age Fotostock
    DO NOT EDIT--Changes must be made through "File info" LONumber=6P1_0610=CorrectionKey=NL-A LESSON 1 Magnetic Forces ©Lluís Real/age fotostock Magnets are able to attract or repel certain materials, such as iron, at a distance. By the end of this lesson . © Houghton Mifflin Harcourt • Image Credits: you will be able to describe the variables that affect the strength and direction of the magnetic force. 96 Unit 2 Electric and Magnetic Forces DO NOT EDIT--Changes must be made through "File info" LONumber=6P1_0610=CorrectionKey=NL-B Go online to view the digital version of the Hands-On Lab for this lesson and to download additional lab resources. CAN YOU EXPLAIN IT? Why do these rings seem to float without touching one another instead of falling? If you were to drop one of these rings onto a peg, you would normally expect it to fall and hit Explore another ring. Instead, when the rings get near one another, they are pushed back up and appear to float. ONLINE! 1. Most objects are not able to float in midair. What must be occurring for these rings to float instead of fall? ©Houghton Mifflin Harcourt 2. What type of force might be affecting the motion of these rings? © Houghton Mifflin Harcourt • Image Credits: © Houghton Mifflin Harcourt • Image Credits: EVIDENCE NOTEBOOK As you explore the lesson, gather evidence to help explain the behavior of the rings. Lesson 1 Magnetic Forces 97 DO NOT EDIT--Changes must be made through “File info” LONumber=6P1_0610=CorrectionKey=NL-B EXPLORATION 1 Describing Magnets and the Magnetic Force A magnet is an object that attracts, or pulls on, Magnet Interactions materials that contain iron.
    [Show full text]
  • Origin of Reduced Magnetization and Domain Formation in Small
    www.nature.com/scientificreports OPEN Origin of reduced magnetization and domain formation in small magnetite nanoparticles Received: 03 January 2017 Zlatko Nedelkoski1, Demie Kepaptsoglou2, Leonardo Lari1, Tianlong Wen3,4, Ryan A. Booth3, Accepted: 07 March 2017 Samuel D. Oberdick3, Pedro L. Galindo5, Quentin M. Ramasse2, Richard F. L. Evans1, Published: 10 April 2017 Sara Majetich3 & Vlado K. Lazarov1 The structural, chemical, and magnetic properties of magnetite nanoparticles are compared. Aberration corrected scanning transmission electron microscopy reveals the prevalence of antiphase boundaries in nanoparticles that have significantly reduced magnetization, relative to the bulk. Atomistic magnetic modelling of nanoparticles with and without these defects reveals the origin of the reduced moment. Strong antiferromagnetic interactions across antiphase boundaries support multiple magnetic domains even in particles as small as 12–14 nm. Magnetic nanoparticles (NPs) are expected to be single magnetic domain below a critical size, typically on the order of the domain wall width for the corresponding bulk material. Single domain particles should have the maximum magnetic moment per volume, which is desirable for their use in ferrofluids1,2, magnetic separation3, contrast agents4,5 for magnetic resonance imaging and magnetic hyperthermia6,7, all of which use iron oxide NPs. However, many researchers observe reduced magnetization, relative to that of the bulk. The reduction has been attributed to surface spin disorder8,9 or to variations in crystallinity, as in the case of low temperature aqueous preparation methods10. However, increasing crystallinity and reducing surface roughness does not necessarily solve this problem11,12. Indeed, in this work we demonstrate that even high quality magnetite NPs can have dra- matic differences in their magnetic properties.
    [Show full text]
  • 7 Magnetic Domain Walls
    7 Magnetic domain walls Poznań 2019 Maciej Urbaniak 7 Magnetic domain walls ● Domain walls in bulk materials cont. ● Domain walls in thin films ● Domain walls in 1D systems ● Domain wall motion Poznań 2019 Maciej Urbaniak Bloch versus Néel wall ● From previous lectures we know Bloch and Néel domain walls. ● Schematic view of the magnetic moments orientation of the Bloch wall in easy plane anisotropy sample ● The magnetic moments rotate gradually about the axis perpendicular to the wall Bloch wall – right or left handedness Chirality – the object cannot be mapped to its mirror image by rotations and translations alone Bloch type wall: The magnetic moments rotate gradually about the axis perpendicular to the wall N éel walls come in two handednesses too. Bloch versus Néel wall ● From previous lectures we know Bloch and Néel domain walls. ● To note is that when the Bloch wall in easy plane anisotropy sample crosses the surface of the sample the magnetic moments within the wall are not parallel to the surface ● Magnetic charges appear on the surface Bloch versus Néel wall ● From previous lectures we know Bloch and Néel domain walls. ● Schematic view of the Néel wall ● Magnetic moments within Néel wall rotate along direction parallel to the wall ● To note is that when the Néel wall in easy plane anisotropy sample crosses the surface of the sample the magnetic moments within the wall are parallel to the surface Bloch versus Néel wall ● The rotation of magnetic moments within the Néel wall creates volume magnetic charges. ● Assuming the following
    [Show full text]
  • Magnetic Domain Configurations of Epitaxial Chromium Dioxide „Cro2… Nanostructures
    APPLIED PHYSICS LETTERS 91, 113512 ͑2007͒ Magnetic domain configurations of epitaxial chromium dioxide „CrO2… nanostructures ͒ Xiaojing Zoua and Gang Xiao Department of Physics, Brown University, Providence, Rhode Island 02912, USA ͑Received 19 July 2007; accepted 24 August 2007; published online 12 September 2007͒ Magnetic domain structures of submicrometric epitaxial CrO2 fabricated using selective-area growth technique were studied by magnetic force microscopy. In-plane, lamellar domain structure with fragmented walls aligned along the magnetic easy axis direction is observed, indicating the existence of a large magnetocrystalline anisotropy. A classical model for ferromagnetic materials with a uniaxial anisotropy was used to explain this domain configuration. Estimates of the domain wall energy density and exchange stiffness constant for CrO2 were obtained. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2784946͔ Spintronics is an emerging area, where the electron spin CrO2 nanostructures with individual feature size smaller than ͑together with the charge͒ plays an active role in storing and 80 nm. transferring information.1 In this area, half-metallic ferro- The experimental process is shown schematically in Fig. magnets have been extensively investigated for realizing 1͑a͒. First, a layer of silicon dioxide was deposited onto the ͑ ͒ spin-dependent devices with high magnetoresistance. These 100 TiO2 substrate and then a 350 nm thick polymethyl- ͑ ͒ materials have a band gap in the minority spin density of methacrylate PMMA was spin coated onto the SiO2 film. states near the Fermi level and therefore exhibit a 100% spin After baking at 185 °C for 30 min, a thin layer of chromium polarization.
    [Show full text]
  • Multiple Tuning of Magnetic Biskyrmionsusing in Situ L-TEM In
    Journal of Physics: Condensed Matter PAPER Multiple tuning of magnetic biskyrmions using in situ L-TEM in centrosymmetric MnNiGa alloy To cite this article: Licong Peng et al 2018 J. Phys.: Condens. Matter 30 065803 View the article online for updates and enhancements. This content was downloaded from IP address 159.226.35.194 on 18/01/2018 at 01:08 IOP Journal of Physics: Condensed Matter Journal of Physics: Condensed Matter J. Phys.: Condens. Matter J. Phys.: Condens. Matter 30 (2018) 065803 (7pp) https://doi.org/10.1088/1361-648X/aaa527 30 Multiple tuning of magnetic biskyrmions 2018 using in situ L-TEM in centrosymmetric © 2018 IOP Publishing Ltd MnNiGa alloy JCOMEL Licong Peng1,2 , Ying Zhang1 , Min He1,2, Bei Ding1,2, Wenhong Wang1 , Jianqi Li1,2, Jianwang Cai1,2, Shouguo Wang3, Guangheng Wu1 065803 and Baogen Shen1,2 1 Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy L Peng et al of Sciences, Beijing 100190, People’s Republic of China 2 School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China 3 School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, People’s Republic of China Printed in the UK E­mail: [email protected] CM Received 17 November 2017, revised 25 December 2017 Accepted for publication 4 January 2018 Published 18 January 2018 10.1088/1361-648X/aaa527 Abstract Magnetic skyrmions are topologically protected spin configurations and have recently received Paper growingly attention in magnetic materials. The existence of biskyrmions within a broad temperature range has been identified in our newly­discovered MnNiGa material, promising for potential application in physics and technological study.
    [Show full text]
  • Magnetism and Interactions Within the Single Domain Limit
    Magnetism and interactions within the single domain limit: reversal, logic and information storage Zheng Li A dissertation Submitted in partial fulfillment of the requirement for the degree of Doctor of Philosophy University of Washington 2015 Reading Committee: Dr. Kannan M. Krishnan, Chair Dr. Karl F. Bohringer Dr. Marjorie Olmstead Program Authorized to Offer Degree: Materials Science & Engineering © Copyright 2015 Zheng Li ABSTRACT Magnetism and interactions within the single domain limit: reversal, logic and information storage Zheng Li Chair of the Supervisory Committee: Dr. Kannan M. Krishnan Materials Science & Engineering Magnetism and magnetic material research on mesoscopic length scale, especially on the size-dependent scaling laws have drawn much attention. From a scientific point of view, magnetic phenomena would vary dramatically as a function of length, corresponding to the multi-single magnetic domain transition. From an industrial point of view, the application of magnetic interaction within the single domain limit has been proposed and studied in the context of magnetic recording and information processing. In this thesis, we discuss the characteristic lengths in a magnetic system resulting from the competition between different energy terms. Further, we studied the two basic interactions within the single domain limit: dipole interaction and exchange interaction using two examples with practical applications: magnetic quantum-dot cellular automata (MQCA) logic and bit patterned media (BPM) magnetic recording. Dipole interactions within the single domain limit for shape-tuned nanomagnet array was studied in this thesis. We proposed a 45° clocking mechanism which would intrinsically eliminate clocking misalignments. This clocking field was demonstrated in both nanomagnet arrays for signal propagation and majority gates for logic operation.
    [Show full text]
  • Visualization of Magnetic Domain Formation in Neodymium Magnet Via Scanning Hard X-Ray Nanoprobe
    Physical Science Research Frontiers 2016 Research Frontiers 2016 Visualization of magnetic domain formation in neodymium magnet via scanning hard X-ray nanoprobe Many kinds of magnets support modern life. Among microscopy (SEM) image of the fractured surface of a them, neodymium magnet (Nd2Fe14B; abbreviated to Nd14.0Fe79.7Cu0.1B6.2 magnet. Approximately 20 grains Nd-Fe-B) is one of the most useful because it is the with diameters of ~5 mm can be seen at the fractured strongest permanent magnet currently available. This surface, where the microstructures are almost material has been applied to various products including conserved as the bulk state. Figures 1(b–d) show high-efficiency electric motors for low-emission hybrid/ XRF images of the same area as the SEM image in electric vehicles, energy-saving air conditioners, and Fig. 1(a). The scan step was 250 nm for all images. The electric power generators. This powerful magnet is SEM and XRF images were obtained with no magnetic regarded as vital for achieving a green society. To field. In the XRF images, elemental distributions of (a) further improve the energy-saving performance of Fe, (b) Nd, and (c) Cu are reproduced. The Nd2Fe14B high-power motors, an alternative permanent magnet main-phases with a high Fe concentration and Nd-rich that can maintain superior performances even at phases adjacent to the Nd2Fe14B main-phase grains high temperatures is still desired. In other words, it is are clearly resolved. Cu is distributed non-uniformly necessary to develop a new magnetic material that has at the boundaries of the Nd2Fe14B main-phase grains.
    [Show full text]
  • 36 Magnetism.Pdf
    Magnetism agnets are fascinating. Bring a pair close together and they snap together and stick. Turn one of the magnets around • and they repel each other. A magnet will stick to a refrigerator door, but it won't stick to an aluminum pan. Magnets come in all shapes and sizes They are popular as toys, A compass points northward because Earth is a giant magnet. are utilized as compasses, and are essential elements in electric motors and generators. Magnetism is very common to everything you see, for it is an essential ingredient of light itself. The term magnetism stems from certain rocks called lodestones found more than 2000 years ago in the region of Magnesia in Greece. In the twelfth century the Chinese used them for navigating ships. In the eighteenth century, the French physicist Charles Coulomb studied the forces between lodestones. We now know that lode- stones contain iron ore, which has been named magnetite. Electricity and magnetism were regarded as unrelated phenom- ena into the early nineteenth century This changed in 1820 when a Danish science professor, Hans Christian Oersted, discovered a rela- tionship between the two while demonstrating electric currents in front of a class of students. When electric current was passed in a wire near a magnetic compass, both Oersted and his students noticed the deflection of the compass needle. This was the connect- ing link that had eluded investigators for decades.* Other discoveries soon followed. Magnets were found to exert forces on current- carrying wires, which led to electric meters and motors. The stage was set for a whole new technology, which would bring electric power, radio, and television.
    [Show full text]
  • Arxiv:0710.0730V1 [Cond-Mat.Mes-Hall] 3 Oct 2007 a Nueaqatzdd Lcrccret N Ieversa
    Fractional Charge and Quantized Current in the Quantum Spin Hall State Xiao-Liang Qi, Taylor L. Hughes, and Shou-Cheng Zhang Department of Physics, McCullough Building, Stanford University, Stanford, CA 94305-4045 To whom correspondence should be addressed: [email protected] (Dated: November 2, 2018) Abstract A profound manifestation of topologically non-trivial states of matter is the occurrence of frac- tionally charged elementary excitations. The quantum spin Hall insulator state is a fundamentally novel quantum state of matter that exists at zero external magnetic field. In this work, we show that a magnetic domain wall at the edge of the quantum spin Hall insulator carries one half of the unit of electron charge, and we propose an experiment to directly measure this fractional charge on an individual basis. We also show that as an additional consequence, a rotating magnetic field can induce a quantized dc electric current, and vice versa. arXiv:0710.0730v1 [cond-mat.mes-hall] 3 Oct 2007 1 Soon after the theoretical proposal of the intrinsic spin Hall effect[1, 2] in doped semicon- ductors, the concept of a time-reversal invariant spin Hall insulator[3] was introduced. In the extreme quantum limit, a quantum spin Hall (QSH) insulator state has been proposed for various systems[4, 5, 6]. The QSH insulators are time-reversal invariant and have a bulk charge-excitation gap. However, this system also possesses topologically protected gapless edge states that lie inside the bulk insulating gap. The edge states of the QSH insulator state differ from the quantum Hall effect and have a distinct helical property: two states with opposite spin-polarization counter-propagate at a given edge[4, 7, 8].
    [Show full text]
  • Magnetic Domain Patterns R.M
    Magnetic domain patterns R.M. Bozorth To cite this version: R.M. Bozorth. Magnetic domain patterns. J. Phys. Radium, 1951, 12 (3), pp.308-321. 10.1051/jphys- rad:01951001203030800. jpa-00234388 HAL Id: jpa-00234388 https://hal.archives-ouvertes.fr/jpa-00234388 Submitted on 1 Jan 1951 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. LE JOURNAL DE PHYSIQUE ET LE RADIUM. TOME 12, MARS 19~1, PAGE 308. MAGNETIC DOMAIN PATTERNS By R. M. BOZORTH, Bell Telephone Laboratories, Murray Hill (New Jersey). Sommaire. 2014 La technique et l’interprétation des diagrammes de poudres magnétiques est briè- vement passée en revue, d’un point de vue historique. Les diagrammes les plus simples observés sont ensuite décrits et expliqués dans la mesure du possible. Dans la troisième Partie, on décrit et discute de nouveaux diagrammes relatifs : a. à un monocristal dont la direction (1 11) est celle de facile aiman- tation (60 pour 100 Co, 40 pour 100 Ni); b. à un monocristal de cobalt; c. à un alliage polycristallin fer-silicium et d. à un alliage polycristallin pour aimants permanents (Alnico 5). Brief revievsr.
    [Show full text]