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

1. Giant Magneto Resistance
GMR

2. The Nobel Prize in Physics 2007The Nobel Prize in Physics 2007
Peter Grünberg
“GMR can be considered one of the first real applications of the
promising field of nanotechnology ”
- Nobel committe
Albert Fert

3. Evolving Technology

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. Magnetic field pointing into
page (screen)
Current-Carrying Wire
Direction of velocity v of
electrons
Direction of force on
conduction electrons

6. Magnetoresistance - MR
 Electrons - moving charges
 Effect of external magnetic field perpendicular
to the flow
 Force due to field pushes electrons off track

7. Concept Behind GMR
• GMR is a completely different effect from
Magnetoresistance (MR)
• MR is the regular “Lorenz” force on charges
moving in a magnetic field
• GMR exploits spin-dependent scattering

8. Spins and Scattering
 An electron moving into a magnetized region
will exhibit spin-dependent scattering
 Scattering depends on direction of spin
GMR is due to intrinsic rotation of the electron
that induces a magnetic moment – the
quantum mechanical property called spin

9. Resistance and magnetization
The straighter the path of the electrons, the greater the
conductance of the material.
Electric resistance is due to electrons diverging from their
straight path when they scatter on irregularities and
impurities in the material.

10. Electron and its spin
•Two types of spin, spin up and spin down
•Spin up exhibited by majority of electrons in ferromagnetic
materials
•Spin down exhibited by small amount of electrons
•Spin up ultimately results in reduction in resistance, while spin
down increases the resistance
•Under the influence of external magnetic field most of the
electrons will be showing spin up so that R reduces

11. Deep into GMR

12. GMR Material
No External Magenetic field
Resistance High
External Magenetic field present
Resistance low

13. Variation of resistance

14. TMR from GMR
The tunnelling process dependent on the available
electron states in the ferromagnetic materials
Ni–SiO2films
Fe/MgO/Fe

15. Merits
• Dramatic Decrease in Price per GB of storage

16. Decrease in size

17. Limitations
GMR applications are limited to
certain specific applications

18. GMR in HDD Technology

19. GMR Based biosensor

21. Other Applications
Magnetoresistive-Based Biosensors

22. Outcomes of GMR
• Discovery of GMR opened the door to a new
field of science, magnetoelectronics (or
spintronics)
• CMR - Colossal MagnetoResistance,
thousand-fold magnetoresistance in La–Ca–
Mn–O
• Magnetoelectronics & Nanotechnology.

23. 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 sensitive
reading head for HDD.

24. References
• J.A. Katine, F.J. Albert, and R.A. Buhrman,
“Current-Driven Magnetization Reversal and
Spin-Wave Excitations in Co/Cu/Co Pillars”
• www.isoloop.com
• www.ieee.org
• https://buffy.eecs.berkeley.edu/PHP/resabs

25. THANK YOU
Presented by
Prashob P K