A Way Forward? (Not necessarily

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A Way Forward?(Not necessarily The Way Forward)

• J N Chapman, University of Glasgow
• Synopsis
• Indicators of activity
• Magnetism in the late 20th century
• A firm base within the UK?
• Some possible ways ahead

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Hard Disc Drive Performance
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The Permanent Magnet Market
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Bonded Magnet Production
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International Magnetics Conferences 1999

• MORIS NdFeB 99
• Hard ferrite magnets ISEM
• Intermag TMRC
• Soft magnetic materials TISD
• Int Conf on Electrical Machines and Drives
• Major sessions at
• MRS APS
• COMPUMAG ISEF
• In the 3 months leading up to this conference,
  Magnews listed 37 conferences!

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Articles in Physics World related to Magnetics-
1999 and 1992

• January - June 1999
• Europe plans magnet facility (1/99)
• Thin films squeeze out domains (1/99)
• Colossal magnetoresistance (2/99)
• Spinning electrons could lead electronics
  revolution (3/99)
• Magnets, molecules and quantum mechanics (3/99)
• Magnetoelectronics (4/99)
• Weak ferromagnet challenges theorists (4/99)
• Faster magnetic memory (6/99)
• January June 1992
• Are environmental magnetic fields dangerous
  (1/92)
• Fundamental effects in a spin (5/92)

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What the Papers Say
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Growth of the UK Magnetics Society
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Magnetism - a Broad Church!

• Magnetic phenomena are studied
• on length scales from nuclear to planetary
• on time scales from fs to geological
• over temperature ranges from ?K to GK
• over field ranges from fT to gt100T
• Magnetics runs through Physics, Chemistry,
  Materials Science, Metallurgy, Engineering, IT.
• There are close materials links to metals and
  oxides, especially superconductors, optical
  materials and semiconductors.
• Generic technologies of importance include thin
  films, growth processing, material
  characterisation.

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Fundamental Physics

• An exciting area of condensed matter science
  involving exotic metals and complex oxides
• Close links to superconductivity
• Extension to lower temperature and higher fields
  reveals wealth of novel behaviour (non-Fermi
  liquid behaviour, quantum fluctuations, magnetic
  quantum oscillations)
• Magnetism in superlattices and magnetic chains
• Interfacial phenomena
• Interface and surface anisotropy
• Spin dependent transport (metal-metal,
  metal-semiconductor, metal- insulator, etc.)
• Tunneling, Coulomb blockade, spin transistor

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Colossal Magnetoresistance

• Based on Mn oxides with the perovskite structure.
• Perovskite structure is natural laboratory for
  studying strongly correlated electron systems
  (coupling between electrons and lattice,
  competition between kinetic energy of mobile
  electrons and repulsive Coulomb interaction,
  etc.) control is achieved by doping.
• Manganites are almost fully polarised.
• Key features include the role of phonons at the
  metal/insulator transition, nature of the
  ground state, effect of interfaces on
  polarisation, phase separation, surface
  magnetisation, local disorder due to doping.
• MR gtgt 100 in fields of a few Tesla.
• Potential for devices? - need for good room
  temperature performance at low fields.
• Defect-free interfaces, introduction of
  controlled defects, exploration of tunneling
  transport in complex oxides having intrinsic
  multilayer structures.

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Magnetic states as a function of doping in
La1-xCaxMnO3
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Giant Magnetoresistance

• GMR arises due to spin-dependent scattering.
• It occurs in magnetic multilayers, granular
  magnetic solids, spin-valves (SVs), spin tunnel
  junctions (STJs). SVs and STJs offer MR values of
  10-40 and sensitivities of few /Oe.
• The basic mechanism is reasonably understood but
  detail is lacking and the GMR effect is not yet
  fully exploited (for example, effect of a domain
  wall at a point contact).
• Application areas are sensors (recording heads,
  positional for automotive application,
  navigational, etc.) and storage (MRAMs).
• Scientific and technological challenges include
• layer thickness control with decreasing stack
  thickness
• exchange biasing of the pinned layer
• performance retention after patterning

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Nanomagnetism

• A branch of nanoscience and technology which
  offers
• new phenomena as the dimensions of a magnetic
  structure fall below various characteristic
  magnetic length scales (e.g. spin diffusion
  length, domain wall width)
• a way of tailoring magnetic properties through
  variation of the size and shape of magnetic
  elements - spin engineering
• Scope for innovation in
• selecting the systems to be patterned and the
  form of the resulting patterned elements
• devising ways in which patterning is carried out
  (advanced lithographies, reactive ion etching,
  mask irradiation, probe microscopies, mass
  replication methods)
• Technological driving forces include ultra-small
  sensors, MRAMs, quantum discs, spintronics.

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Recording

• Magnetic recording - hard disc and tape
• Phenomenal growth over the last decade due to
  near-insatiable demands to store data.
• Key issues now are what limits the density at
  which we can store information, the time
  required to write and access it and the period of
  time over which the medium retains it.
• Challenges span materials with improved magnetic
  properties, through developing sophisticated
  micromechanical drives, to optimisation of the
  recording channel and coding.
• As recording densities increase beyond
  70GB/sq.in, and for special applications, other
  technologies may be/are required
• recording on perpendicular media or discrete
  media (quantum discs), magneto- optic recording,
  hybrid magnetic - MO recording, magnetic random
  access memory (MRAM)

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MRAM cells showing architecture
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Spintronics

• Spintronics encompasses GMR, spin-dependent
  tunneling and spin-injection devices.
• MRAM
• non-volatile, radiation hard, speed of SRAM
  (lt3ns), density of DRAM, low power (0.005x), low
  cost (0.1x), infinitely cyclable
• Coherent spin transport in semiconductors looks
  encouraging following 2 recent discoveries
• at room temperature, optically induced
  spin-states have been found to be very long
  lived
• ferromagnetism exists in semiconducting GaMnAs
• Once the physics and materials aspects are
  solved, spin enhanced and enabled electronics,
  spin filters, spin FETs, quantum
  spin-electronics, coherent spin electronics are
  anticipated.

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Control and Measurement of Material Properties

• Control through growth conditions, processing and
  patterning
• Final performance depends on interplay between
  intrinsic and extrinsic properties
• Strong role for theory and modelling in a
  multi-parameter space
• Increased need to measure both structural and
  magnetic properties as completely as possible
• Importance of interfaces
• Understanding and exploitation of MR phenomena
  (depolarisation of carriers in GMR and
  especially CMR materials)
• Control of surface anisotropies (property
  control in ultra-thin films)
• Coupling between grains in hard magnetic
  materials and ultra-high density recording media

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Characterisation Techniques

• In-house characterisation
• Ultra-fast measurements (pump-probe - sub-ps)
• High spatial resolution imaging (MFM with novel
  sensor heads, in-situ TEM)
• Sophisticated magnetometry (micro-magnetometers,
  minor loops, time dependence over decades)
• In-situ and ex-situ analytical techniques
  (spin-polarised techniques, STM, AFM, Auger,
  EELS)
• Characterisation using Facilities
• Neutrons, X-rays, Ultra-high fields

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TEM Magnetic Images of NiFe Elements(Courtesy of
Dr K Kirk, University of Glasgow)
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MFM images of 50nm tracks(Courtesy of Dr L
Folks, IBM)
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Facilities

• X-ray magnetic scattering
• Resonant enhancement of magnetic scattering,
  element specific magnetic studies
• Dichroism studies (circular and linearly
  polarised), x-ray microscopy
• Separation of spin and orbit contributions to
  the magnetic behaviour of materials
• 100T magnet - pulsed fields 10ms duration
• Investigation of new physics along the field
  axis of the phase diagram
• Understanding in strongly correlated electronic
  systems of the underlying many-body physics,
  including magnetic quantum critical phenomena
• Application to high anisotropy intermetallics,
  metallic superlattices, doped oxides,
  spin-liquids

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Permanent Magnets

• Rare earth - transition metal magnets (Fe and
  Co-based) are the subject of most research.
• Annual growth rate of sintered NdFeB magnets
  12, of bonded NdFeB magnets 20
• Partly fuelled by global growth of PCs but other
  areas promising including MRI, industrial
  robotics, mobile phones
• Largest potential is in electric vehicles
• Challenges include
• Materials suitable for operation at high
  temperature (180C)
• Improved corrosion resistance
• Cost-effective production methods, recalling
  that the microstructure dominates the properties
  of permanent magnet materials

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Some of the Many Applications of Permanent Magnets

• Automotive
• Starter motors, anti-lock braking systems (ABS),
  motor drives for wipers, injection pumps, fans
  and controls for windows, seats etc,
  loudspeakers, eddy current breaks, alternators
• Telecommunications
• Loudspeakers, microphones, telephone ringers,
  electro-acoustic pick-ups, switches and relays
• Data Processing
• Discs drives and actuators, stepping motors,
  printers
• Consumer Electronics
• DC motors for showers, washing machines, drills,
  citrus presses, knife sharpeners, food mixers,
  can openers, hair trimmers etc., low voltage DC
  drives for cordless appliances such as drills,
  hedgecutters, chainsaws, magnetic locks for
  cupboards and doors, loudspeakers for TV and
  audio, TV beam correction and focusing device,
  compact-disc drives, home computers, video
  recorders, electric clocks, analogue watches
• Electronic and Instrumentation
• Sensors, contactless switches, NMR spectrometer,
  energy meter disc, electro-mechanical
  transducers, crossed field tubes, flux-transfer
  trip device,
• Industrial
• DC motors for magnetic tools, robotics, magnetic
  separators for extracting metals and ores,
  magnetic bearings, servo-motor drives, lifting
  apparatus, brakes and clutches, meters and
  measuring equipment
• Astro and Aerospace
• Frictionless bearings, stepping motors,
  couplings, instrumentation, travelling wave
  tubes, auto-compass
• Biosurgical
• Dentures, orthopaedics, wound closures, stomach
  seals, repulsion collars, ferromagnetic probes,
  cancer cell separators, NMR body scanner

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Soft Magnetic Materials

• Progress continues in FeSi and in soft amorphous
  and nanocrystalline alloys
• The scale of use of FeSi makes reductions of loss
  of a fraction of 1 significant
• (Fe, Co, Ni)(Si, B) plus additions are developed
  for specialist applications and there is scope
  for innovation here
• Modelling on various length scales
  (micromagnetic, hysteresis and finite element)
  and finding ways of linking them will lead to
  more efficient machines and motors
• Understanding how materials respond under varying
  combinations of field and stress is
  scientifically challenging and is the key to new
  and improved applications
• Amorphous wires with near zero magnetostriction
  and with a strong negative magnetostriction offer
  exciting possibilities for many sensor
  applications through the giant magneto-impedance
  and the stress impedance effect

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Machines, Drives and Actuators

• Improved performance, increased energy efficiency
  and the enabling of applications not previously
  possible is being realised with the help of
• advanced magnetic materials
• powerful design and analysis programmes
• Examples of innovation include
• embedded machines in aero engines operating at
  high temperatures, with magnetic bearings
  replacing mechanical bearings
• soft, high-resistivity composites for magnetic
  bearings running at up to 60,000rpm in vacuum
  with appropriate magnetic circuit design
  hysteresis is almost eliminated and losses are
  minimised
• multi-degree of freedom actuators incorporating
  high energy product magnets and operating at
  200Hz for force feedback joysticks usable in
  surgery and other active vision systems,
  including computer games

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Innovations in Machines(Courtesy of Dr G Jewell
and Professor D Howe, University of Sheffield)

• High Temperature (800oC) Linear Actuator
• 24 Cobalt Iron
• Ceramic Insulated, Nickel plated copper windings
• 300N, ?0.5mm stroke
• Linear permanent magnet actuator
• for textile machinery
• 200mm stroke
• Peak acceleration of 100g

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Innovations in Machines(Courtesy of Dr G Jewell
and Professor D Howe, University of Sheffield)

• Aerospace Electrohydraulic surface actuator
• Technology Demonstrator for Airbus A3XX
• 55kW, Brushless NdFeB Permanent Magnet Motor
• Brushless Permanent Magnet Machine
• 120,000rpm (100mm OD)
• Carbon Fibre / NdFeB / Epoxy composite rotor

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Magnetics in the United Kingdom

• There are scientific, technical and engineering
  opportunities in profusion - how can the UK take
  best advantage?
• UK background
• The total number of workers in academia and
  industry in magnetism is considerable (for
  example, there are ?500 academic researchers).
• With a few notable exceptions, activity is
  concentrated in small units in industry and
  academia.
• There is a danger of sub-criticality.
• Collaboration and networking are seen as the
  best way of avoiding the danger of
  sub-criticality.

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Organisations with an Interest in Fostering the
Advancement of UK Magnetics

• Learned societies and industrial clubs/trade
  associations - IoP, IoM, IEE, IEEE, UK MagSoc,
  TRIUMF. (for example Joint Magnetics Workshop)
• DTI (LINK scheme in Storage and Displays, UKISC)
• Foresight
• Seagate Technology Plan
• Europe Framework 5 (opportunities for links to
  elsewhere in Europe)
• EPSRC

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Possible LINK in Information Storage and Display

• Objectives
• Encourage new links between companies and
  science engineering base
• Involve gt 20 organisations (including gt 10 SMEs)
  in collaborative projects
• Stimulate exploitation of academic research
• Encourage supplier-user and small - large
  company relationships
• Develop UK information storage community
• Proposed budget
• 8M plus matching funds from industry
• Proposed launch
• End 1999/beginning 2000

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EPSRC (I)

• Magnetism and Magnetic Materials Initiative (1989
  - 1994)
• Advanced Magnetics Programme (Physics and
  Materials) - due to end 2000
• Machines and Drives (Engineering) - ended 1998
• Responsive mode (notable take-up in fundamental
  condensed matter physics) - continuing
• What next?
• The next 6 months provide an opportunity for you
  to advise programmes managers of what you would
  like to happen and why!

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EPSRC (II)

• Another managed programme?
• Bad fit to current EPSRC policy but would
  protect those aspects of the programme at the
  physics/materials materials/engineering
  interfaces which arguably contain some of the
  most exciting possibilities for the future.
• Return to responsive modes in Physics, Materials
  and Engineering?
• Encourage EPSRC to ensure that assessment panels
  are chosen which contain representatives from
  more than one programme area.

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EPSRC (III)

• If there is no EPSRC coordinator, will the UK
  (academic) magnetics community fragment?
• Suggestion
• Establish EPSRC Networks involving both
  academics and industrialists.
• Use these as fora to decide (non-exclusive)
  priorities for different aspects of magnetics.
• Set aside some of final round of AMP money to
  fund these.
• Purpose
• Help carry forward existing collaborations and
  provide springboard for new ones so that small
  individual groups can make maximum impact.
• Provide a harmonious way to keep UK magnetics
  competitive and at the leading edge.

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Conclusions

• At the end of the 1980s UK magnetics was weak
  at the end of the 1990s this is no longer the
  case.
• The momentum and cohesion built up over the last
  decade must not be allowed to evaporate.
• A diffuse non-interacting academic community will
  never maintain a high profile with government,
  industry, EPSRC and is unlikely to make an impact
  internationally.
• Significant organisational change (for academics
  at least) is inevitable in the next 12 months but
  there is a short time window open to try to
  influence the nature of the change this
  opportunity must be taken!