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
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
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
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