Chapter 2 Magnetic Domain Theory in Static
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Basic Magnetic Measurement Methods
Basic magnetic measurement methods Magnetic measurements in nanoelectronics 1. Vibrating sample magnetometry and related methods 2. Magnetooptical methods 3. Other methods Introduction Magnetization is a quantity of interest in many measurements involving spintronic materials ● Biot-Savart law (1820) (Jean-Baptiste Biot (1774-1862), Félix Savart (1791-1841)) Magnetic field (the proper name is magnetic flux density [1]*) of a current carrying piece of conductor is given by: μ 0 I dl̂ ×⃗r − − ⃗ 7 1 - vacuum permeability d B= μ 0=4 π10 Hm 4 π ∣⃗r∣3 ● The unit of the magnetic flux density, Tesla (1 T=1 Wb/m2), as a derive unit of Si must be based on some measurement (force, magnetic resonance) *the alternative name is magnetic induction Introduction Magnetization is a quantity of interest in many measurements involving spintronic materials ● Biot-Savart law (1820) (Jean-Baptiste Biot (1774-1862), Félix Savart (1791-1841)) Magnetic field (the proper name is magnetic flux density [1]*) of a current carrying piece of conductor is given by: μ 0 I dl̂ ×⃗r − − ⃗ 7 1 - vacuum permeability d B= μ 0=4 π10 Hm 4 π ∣⃗r∣3 ● The Physikalisch-Technische Bundesanstalt (German national metrology institute) maintains a unit Tesla in form of coils with coil constant k (ratio of the magnetic flux density to the coil current) determined based on NMR measurements graphics from: http://www.ptb.de/cms/fileadmin/internet/fachabteilungen/abteilung_2/2.5_halbleiterphysik_und_magnetismus/2.51/realization.pdf *the alternative name is magnetic induction Introduction It -
Magnetism, Magnetic Properties, Magnetochemistry
Magnetism, Magnetic Properties, Magnetochemistry 1 Magnetism All matter is electronic Positive/negative charges - bound by Coulombic forces Result of electric field E between charges, electric dipole Electric and magnetic fields = the electromagnetic interaction (Oersted, Maxwell) Electric field = electric +/ charges, electric dipole Magnetic field ??No source?? No magnetic charges, N-S No magnetic monopole Magnetic field = motion of electric charges (electric current, atomic motions) Magnetic dipole – magnetic moment = i A [A m2] 2 Electromagnetic Fields 3 Magnetism Magnetic field = motion of electric charges • Macro - electric current • Micro - spin + orbital momentum Ampère 1822 Poisson model Magnetic dipole – magnetic (dipole) moment [A m2] i A 4 Ampere model Magnetism Microscopic explanation of source of magnetism = Fundamental quantum magnets Unpaired electrons = spins (Bohr 1913) Atomic building blocks (protons, neutrons and electrons = fermions) possess an intrinsic magnetic moment Relativistic quantum theory (P. Dirac 1928) SPIN (quantum property ~ rotation of charged particles) Spin (½ for all fermions) gives rise to a magnetic moment 5 Atomic Motions of Electric Charges The origins for the magnetic moment of a free atom Motions of Electric Charges: 1) The spins of the electrons S. Unpaired spins give a paramagnetic contribution. Paired spins give a diamagnetic contribution. 2) The orbital angular momentum L of the electrons about the nucleus, degenerate orbitals, paramagnetic contribution. The change in the orbital moment -
Magnetic Force Microscopy of Superparamagnetic Nanoparticles
Magnetic Force Microscopy of Superparamagnetic Nanoparticles for Biomedical Applications Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Tanya M. Nocera, M.S. Graduate Program in Biomedical Engineering The Ohio State University 2013 Dissertation Committee: Gunjan Agarwal, PhD, Advisor Stephen Lee, PhD Jessica Winter, PhD Anil Pradhan, PhD Copyright by Tanya M. Nocera 2013 Abstract In recent years, both synthetic as well as naturally occurring superparamagnetic nanoparticles (SPNs) have become increasingly important in biomedicine. For instance, iron deposits in many pathological tissues are known to contain an accumulation of the superparamagnetic protein, ferritin. Additionally, man-made SPNs have found biomedical applications ranging from cell-tagging in vitro to contrast agents for in vivo diagnostic imaging. Despite the widespread use and occurrence of SPNs, detection and characterization of their magnetic properties, especially at the single-particle level and/or in biological samples, remains a challenge. Magnetic signals arising from SPNs can be complicated by factors such as spatial distribution, magnetic anisotropy, particle aggregation and magnetic dipolar interaction, thereby confounding their analysis. Techniques that can detect SPNs at the single particle level are therefore highly desirable. The goal of this thesis was to develop an analytical microscopy technique, namely magnetic force microscopy (MFM), to detect and spatially localize synthetic and natural SPNs for biomedical applications. We aimed to (1) increase ii MFM sensitivity to detect SPNs at the single-particle level and (2) quantify and spatially localize iron-ligated proteins (ferritin) in vitro and in biological samples using MFM. -
Coey-Slides-1.Pdf
These lectures provide an account of the basic concepts of magneostatics, atomic magnetism and crystal field theory. A short description of the magnetism of the free- electron gas is provided. The special topic of dilute magnetic oxides is treated seperately. Some useful books: • J. M. D. Coey; Magnetism and Magnetic Magnetic Materials. Cambridge University Press (in press) 600 pp [You can order it from Amazon for £ 38]. • Magnétisme I and II, Tremolet de Lachesserie (editor) Presses Universitaires de Grenoble 2000. • Theory of Ferromagnetism, A Aharoni, Oxford University Press 1996 • J. Stohr and H.C. Siegmann, Magnetism, Springer, Berlin 2006, 620 pp. • For history, see utls.fr Basic Concepts in Magnetism J. M. D. Coey School of Physics and CRANN, Trinity College Dublin Ireland. 1. Magnetostatics 2. Magnetism of multi-electron atoms 3. Crystal field 4. Magnetism of the free electron gas 5. Dilute magnetic oxides Comments and corrections please: [email protected] www.tcd.ie/Physics/Magnetism 1 Introduction 2 Magnetostatics 3 Magnetism of the electron 4 The many-electron atom 5 Ferromagnetism 6 Antiferromagnetism and other magnetic order 7 Micromagnetism 8 Nanoscale magnetism 9 Magnetic resonance Available November 2009 10 Experimental methods 11 Magnetic materials 12 Soft magnets 13 Hard magnets 14 Spin electronics and magnetic recording 15 Other topics 1. Magnetostatics 1.1 The beginnings The relation between electric current and magnetic field Discovered by Hans-Christian Øersted, 1820. ∫Bdl = µ0I Ampère’s law 1.2 The magnetic moment Ampère: A magnetic moment m is equivalent to a current loop. Provided the current flows in a plane m = IA units Am2 In general: m = (1/2)∫ r × j(r)d3r where j is the current density; I = j.A so m = 1/2∫ r × Idl = I∫ dA = m Units: Am2 1.3 Magnetization Magnetization M is the local moment density M = δm/δV - it fluctuates wildly on a sub-nanometer and a sub-nanosecond scale. -
Two-Dimensional Field-Sensing Map and Magnetic Anisotropy Dispersion
PHYSICAL REVIEW B 83, 144416 (2011) Two-dimensional field-sensing map and magnetic anisotropy dispersion in magnetic tunnel junction arrays Wenzhe Zhang* and Gang Xiao† Department of Physics, Brown University, Providence, Rhode Island 02912, USA Matthew J. Carter Micro Magnetics, Inc., 617 Airport Road, Fall River, Massachusetts 02720, USA (Received 22 July 2010; revised manuscript received 24 January 2011; published 22 April 2011) Due to the inherent disorder in local structures, anisotropy dispersion exists in almost all systems that consist of multiple magnetic tunnel junctions (MTJs). Aided by micromagnetic simulations based on the Stoner-Wohlfarth (S-W) model, we used a two-dimensional field-sensing map to study the effect of anisotropy dispersion in MTJ arrays. First, we recorded the field sensitivity value of an MTJ array as a function of the easy- and hard-axis bias fields, and then extracted the anisotropy dispersion in the array by comparing the experimental sensitivity map to the simulated map. Through a mean-square-error-based image processing technique, we found the best match for our experimental data, and assigned a pair of dispersion numbers (anisotropy angle and anisotropy constant) to the array. By varying each of the parameters one at a time, we were able to discover the dependence of field sensitivity on magnetoresistance ratio, coercivity, and magnetic anisotropy dispersion. The effects from possible edge domains are also discussed to account for a correction term in our analysis of anisotropy angle distribution using the S-W model. We believe this model is a useful tool for monitoring the formation and evolution of anisotropy dispersion in MTJ systems, and can facilitate better design of MTJ-based devices. -
Magnetization and Demagnetization Studies of a HTS Bulk in an Iron Core Kévin Berger, Bashar Gony, Bruno Douine, Jean Lévêque
Magnetization and Demagnetization Studies of a HTS Bulk in an Iron Core Kévin Berger, Bashar Gony, Bruno Douine, Jean Lévêque To cite this version: Kévin Berger, Bashar Gony, Bruno Douine, Jean Lévêque. Magnetization and Demagnetization Stud- ies of a HTS Bulk in an Iron Core. IEEE Transactions on Applied Superconductivity, Institute of Electrical and Electronics Engineers, 2016, 26 (4), pp.4700207. 10.1109/TASC.2016.2517628. hal- 01245678 HAL Id: hal-01245678 https://hal.archives-ouvertes.fr/hal-01245678 Submitted on 19 Dec 2015 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. 1PoBE_12 1 Magnetization and Demagnetization Studies of a HTS Bulk in an Iron Core Kévin Berger, Bashar Gony, Bruno Douine, and Jean Lévêque Abstract—High Temperature Superconductors (HTS) are large quantity, with good and homogeneous properties, they promising materials in variety of practical applications due to are still the most promising materials for the applications of their ability to act as powerful permanent magnets. Thus, in this superconductors. paper, we have studied the influence of some pulsed and There are several ways to magnetize HTS bulks; but we pulsating magnetic fields applied to a magnetized HTS bulk assume that the most convenient one is to realize a method in sample. -
Apparatus for Magnetization and Efficient Demagnetization of Soft
3274 IEEE TRANSACTIONS ON MAGNETICS, VOL. 45, NO. 9, SEPTEMBER 2009 Apparatus for Magnetization and Efficient Demagnetization of Soft Magnetic Materials Paul Oxley Physics Department, The College of the Holy Cross, Worcester, MA 01610 USA This paper describes an electrical circuit that can be used to automatically magnetize and ac-demagnetize moderately soft magnetic materials and with minor modifications could be used to demagnetize harder magnetic materials and magnetic geological samples. The circuit is straightforward to replicate, easy to use, and low in cost. Independent control of the demagnetizing current frequency, am- plitude, and duration is available. The paper describes the circuit operation in detail and shows that it can demagnetize a link-shaped specimen of 430FR stainless steel with 100% efficiency. Measurements of the demagnetization efficiency of the specimen with different ac-demagnetization frequencies are interpreted using eddy-current theory. The experimental results agree closely with the theoretical predictions. Index Terms—Demagnetization, demagnetizer, eddy currents, magnetic measurements, magnetization, residual magnetization. I. INTRODUCTION to magnetize a magnetic sample by delivering a current propor- HERE is a widespread need for a convenient and eco- tional to an input voltage provided by the user and can be used T nomical apparatus that can ac-demagnetize magnetic ma- to measure magnetic properties such as - hysteresis loops terials. It is well known that to accurately measure the mag- and magnetic permeability. netic properties of a material, it must first be in a demagnetized Our apparatus is simple, easy to use, and economical. It state. For this reason, measurements of magnetization curves uses up-to-date electronic components, unlike many previous and hysteresis loops use unmagnetized materials [1], [2] and it designs [9]–[13], which therefore tend to be rather compli- is thought that imprecise demagnetization is a leading cause for cated. -
Tailored Magnetic Properties of Exchange-Spring and Ultra Hard Nanomagnets
Max-Planck-Institute für Intelligente Systeme Stuttgart Tailored Magnetic Properties of Exchange-Spring and Ultra Hard Nanomagnets Kwanghyo Son Dissertation An der Universität Stuttgart 2017 Tailored Magnetic Properties of Exchange-Spring and Ultra Hard Nanomagnets Von der Fakultät Mathematik und Physik der Universität Stuttgart zur Erlangung der Würde eines Doktors der Naturwissenschaften (Dr. rer. nat.) genehmigte Abhandlung Vorgelegt von Kwanghyo Son aus Seoul, SüdKorea Hauptberichter: Prof. Dr. Gisela Schütz Mitberichter: Prof. Dr. Sebastian Loth Tag der mündlichen Prüfung: 04. Oktober 2017 Max‐Planck‐Institut für Intelligente Systeme, Stuttgart 2017 II III Contents Contents ..................................................................................................................................... 1 Chapter 1 ................................................................................................................................... 1 General Introduction ......................................................................................................... 1 Structure of the thesis ....................................................................................................... 3 Chapter 2 ................................................................................................................................... 5 Basic of Magnetism .......................................................................................................... 5 2.1 The Origin of Magnetism ....................................................................................... -
Understanding the Origin of Magnetocrystalline Anisotropy in Pure and Fe/Si Substituted Smco5
Understanding the origin of magnetocrystalline anisotropy in pure and Fe/Si substituted SmCo5 *Rajiv K. Chouhan1,2,3, A. K. Pathak3, and D. Paudyal3 1CNR-NANO Istituto Nanoscienze, Centro S3, I-41125 Modena, Italy 2Harish-Chandra Research Institute, HBNI, Jhunsi, Allahabad 211019, India 3The Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, IA 50011–3020, USA We report magnetocrystalline anisotropy of pure and Fe/Si substituted SmCo5. The calculations were performed using the advanced density functional theory (DFT) including onsite electron-electron correlation and spin orbit coupling. Si substitution substantially reduces both uniaxial magnetic anisotropy and magnetic moment. Fe substitution with the selective site, on the other hand, enhances the magnetic moment with limited chemical stability. The magnetic hardness of SmCo5 is governed by Sm 4f localized orbital contributions, which get flatten and split with the substitution of Co (2c) with Si/Fe atoms, except the Fe substitution at 3g site. It is also confirmed that Si substitutions favor the thermodynamic stability on the contrary to diminishing the magnetic and anisotropic effect in SmCo5 at either site. INTRODUCTION Search for high-performance permanent magnets is always being a challenging task for modern technological applications as they are key driving components for propulsion motors, wind turbines and several other direct or indirect market consumer products. Curie temperature Tc, magnetic anisotropy, and saturation magnetization Ms, of the materials, are some basic fundamental properties used to classify the permanent magnets. At Curie temperature a material loses its ferromagnetic properties, hence higher the Tc, better is the magnets to be used under extreme conditions. -
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. -
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. -
Superparamagnetism and Magnetic Properties of Ni Nanoparticles Embedded in Sio2
PHYSICAL REVIEW B 66, 104406 ͑2002͒ Superparamagnetism and magnetic properties of Ni nanoparticles embedded in SiO2 F. C. Fonseca, G. F. Goya, and R. F. Jardim* Instituto de Fı´sica, Universidade de Sa˜o Paulo, CP 66318, 05315-970, Sa˜o Paulo, SP, Brazil R. Muccillo Centro Multidisciplinar de Desenvolvimento de Materiais Ceraˆmicos CMDMC, CCTM-Instituto de Pesquisas Energe´ticas e Nucleares, CP 11049, 05422-970, Sa˜o Paulo, SP, Brazil N. L. V. Carren˜o, E. Longo, and E. R. Leite Centro Multidisciplinar de Desenvolvimento de Materiais Ceraˆmicos CMDMC, Departamento de Quı´mica, Universidade Federal de Sa˜o Carlos, CP 676, 13560-905, Sa˜o Carlos, SP, Brazil ͑Received 4 March 2002; published 6 September 2002͒ We have performed a detailed characterization of the magnetic properties of Ni nanoparticles embedded in a SiO2 amorphous matrix. A modified sol-gel method was employed which resulted in Ni particles with ϳ Ϸ average radius 3 nm, as inferred by TEM analysis. Above the blocking temperature TB 20 K for the most diluted sample, magnetization data show the expected scaling of the M/M S vs H/T curves for superparamag- netic particles. The hysteresis loops were found to be symmetric about zero field axis with no shift via Ͻ exchange bias, suggesting that Ni particles are free from an oxide layer. For T TB the magnetic behavior of these Ni nanoparticles is in excellent agreement with the predictions of randomly oriented and noninteracting magnetic particles, as suggested by the temperature dependence of the coercivity field that obeys the relation ϭ Ϫ 1/2 ϳ HC(T) HC0͓1 (T/TB) ͔ below TB with HC0 780 Oe.