Evaluation of the Magnetocrystalline Anisotropy of Typical Materials Using MBN Technology
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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. -
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. -
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. -
Magnetic Anisotropy and Exchange in (001) Textured Fept-Based Nanostructures
University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Theses, Dissertations, and Student Research: Department of Physics and Astronomy Physics and Astronomy, Department of 12-2013 Magnetic Anisotropy and Exchange in (001) Textured FePt-based Nanostructures Tom George University of Nebraska-Lincoln, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/physicsdiss Part of the Condensed Matter Physics Commons George, Tom, "Magnetic Anisotropy and Exchange in (001) Textured FePt-based Nanostructures" (2013). Theses, Dissertations, and Student Research: Department of Physics and Astronomy. 31. https://digitalcommons.unl.edu/physicsdiss/31 This Article is brought to you for free and open access by the Physics and Astronomy, Department of at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Theses, Dissertations, and Student Research: Department of Physics and Astronomy by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. MAGNETIC ANISOTROPY AND EXCHANGE IN (001) TEXTURED FePt-BASED NANOSTRUCTURES by Tom Ainsley George A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy Major: Physics and Astronomy Under the Supervision of Professor David J. Sellmyer Lincoln, Nebraska December, 2013 MAGNETIC ANISOTROPY AND EXCHANGE IN (001) TEXTURED FePt-BASED NANOSTRUCTURES Tom Ainsley George, Ph.D. University of Nebraska, 2013 Adviser: David J. Sellmyer Hard-magnetic L10 phase FePt has been demonstrated as a promising candidate for future nanomagnetic applications, especially magnetic recording at areal densities approaching 10 Tb/in2. Realization of FePt’s potential in recording media requires control of grain size and intergranular exchange interactions in films with high degrees of L10 order and (001) crystalline texture, including high perpendicular magnetic anisotropy. -
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. -
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. -
Magnetic Dynamics of Single Domain Ni Nanoparticles
J. Appl. Phys. 93, 6531 (2003); doi:10.1063/1.1540032 (3 pages) AF-13 Magnetic dynamics of single domain Ni nanoparticles G. F. Goya, F.C. Fonseca, and R. F. Jardim Instituto de Física, Universidade de São Paulo, CP 66318, 05315-970, São Paulo, Brazil R. Muccillo Centro Multidisciplinar de Desenvolvimento de Materiais Cerâmicos CMDMC, CCTM-Instituto de Pesquisas Energéticas e Nucleares CP 11049, 05422-970, São Paulo, SP, Brazil N. L. V. Carreño, E. Longo, and E.R. Leite Centro Multidisciplinar de Desenvolvimento de Materiais Cerâmicos CMDMC, Departamento de Química, Universidade Federal de São Carlos CP 676, 13560-905, São Carlos, SP, Brazil The dynamic magnetic properties of Ni nanoparticles diluted in an amorphous SiO2 matrix prepared from a modified sol-ge l me thod have been studied by the frequency f dependence of the ac magnetic susceptibility χ(T). For samples with similar average radii ~ 3-4 nm, an increase of the blocking temperature from TB ~ 20 to ~ 40 K was observed for Ni concentrations of ~ 1.5 and 5 wt.%, respectively, assigned to the effects of dipolar interactions. Both the in-phase χ’(T) and the out-of- phase χ’’(T) maxima follow the predictions of the thermally activated Néel-Arrhenius model. The effective magnetic anisotropy constant Keff inferred from χ’’(T) versus f data for the 1.5 wt.% Ni sample is close to the value of the magnetocrystalline anisotropy of bulk Ni, suggesting that surface effects are negligible in the present samples. In addition, the contribution from dipolar interactions to the total anisotropy energy Ea in specimens with 5 wt.% Ni was found to be comparable to the intrinsic magnetocrystalline anisotropy barrier.