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Gmr

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The concept, application of Giant Magneto Resistance is being discussed in the slides
The discovery of this phenomenon has caused vast developments in the field of spintronics

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Gmr

  1. 1. Giant Magneto ResistanceGMR
  2. 2. The Nobel Prize in Physics 2007The Nobel Prize in Physics 2007Peter Grünberg“GMR can be considered one of the first real applications of thepromising field of nanotechnology ”- Nobel committeAlbert Fert
  3. 3. Evolving Technology
  4. 4. Magnetic Forces Mathematically,FB = qv x B|FB| = |qv| |B| sin θ( θ is angle between v and B)direction given by right-hand rule
  5. 5. Magnetic field pointing intopage (screen)Current-Carrying WireDirection of velocity v ofelectronsDirection of force onconduction electrons
  6. 6. Magnetoresistance - MR Electrons - moving charges Effect of external magnetic field perpendicularto the flow Force due to field pushes electrons off track
  7. 7. Concept Behind GMR• GMR is a completely different effect fromMagnetoresistance (MR)• MR is the regular “Lorenz” force on chargesmoving in a magnetic field• GMR exploits spin-dependent scattering
  8. 8. Spins and Scattering An electron moving into a magnetized regionwill exhibit spin-dependent scattering Scattering depends on direction of spinGMR is due to intrinsic rotation of the electronthat induces a magnetic moment – thequantum mechanical property called spin
  9. 9. Resistance and magnetizationThe straighter the path of the electrons, the greater theconductance of the material.Electric resistance is due to electrons diverging from theirstraight path when they scatter on irregularities andimpurities in the material.
  10. 10. Electron and its spin•Two types of spin, spin up and spin down•Spin up exhibited by majority of electrons in ferromagneticmaterials•Spin down exhibited by small amount of electrons•Spin up ultimately results in reduction in resistance, while spindown increases the resistance•Under the influence of external magnetic field most of theelectrons will be showing spin up so that R reduces
  11. 11. Deep into GMR
  12. 12. GMR MaterialNo External Magenetic fieldResistance HighExternal Magenetic field presentResistance low
  13. 13. Variation of resistance
  14. 14. TMR from GMRThe tunnelling process dependent on the availableelectron states in the ferromagnetic materialsNi–SiO2filmsFe/MgO/Fe
  15. 15. Merits• Dramatic Decrease in Price per GB of storage
  16. 16. Decrease in size
  17. 17. LimitationsGMR applications are limited tocertain specific applications
  18. 18. GMR in HDD Technology
  19. 19. GMR Based biosensor
  20. 20. Other ApplicationsMagnetoresistive-Based Biosensors
  21. 21. Outcomes of GMR• Discovery of GMR opened the door to a newfield of science, magnetoelectronics (orspintronics)• CMR - Colossal MagnetoResistance,thousand-fold magnetoresistance in La–Ca–Mn–O• Magnetoelectronics & Nanotechnology.
  22. 22. SummarySummary• GMR effects was discovered by A. FertA. Fert and P.P.GrünbergGrünberg independently.• GMR shows large magnetoresistance.– GMR ~50 % > MR ~ a few %• The greatest contribution of GMR is the sensitivereading head for HDD.
  23. 23. References• J.A. Katine, F.J. Albert, and R.A. Buhrman,“Current-Driven Magnetization Reversal andSpin-Wave Excitations in Co/Cu/Co Pillars”• www.isoloop.com• www.ieee.org• https://buffy.eecs.berkeley.edu/PHP/resabs
  24. 24. THANK YOUPresented byPrashob P K

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