Giant magnetoresistance (GMR) is a quantum effect observed in thin film structures with alternating ferromagnetic and nonmagnetic layers that can control electrical resistance at the nanoscale using magnetic fields. It was discovered in the late 1980s by Peter Grunberg and Albert Fert working independently, for which they received the Nobel Prize. GMR results from electron spin and magnetic moments, causing more or less scattering depending on whether the magnetic moments are parallel or antiparallel. This effect is observed at the nanoscale where the electron mean free path is greater than the interlayer separation. Main applications of GMR include magnetic field sensors for hard drives, biosensors, and MRAM as it allows control of electrical resistance with magnetic fields

1. Presented To,
Dr.Naeem Ahmed
Submitted by,
Jamil Ahmed. (642/fbas/s14.bs-physics.)

2. Giant magnetoresistance.
 Giant magnetoresistance (GMR) is a quantum
magnetorisitance effect observed in thin film
structures composed of alternating ferromagnetic
and non magnetic layers.
 It is also a way to
control the electrical
resistance at the nano
scale using magnetic field.

3. Discovery of GMR.
 The Giant magnetoresistive (GMR) effect was
discovered in the late 1980s by two European scientists
working independently.
 Awarded jointly to Peter Grunberg and Albert Fert
Peter Grunberg Albert Fert

4. Discovery of GMR.
 Multilayer's of Fe/Cr prepared
by molecular beam.
 Fe is ferromagnetic
 material can be
 permanently magnetized.
 Cr is non-magnetic.
 Magnetoresistive
effect -50%.

5. Basic Theory.
 Electron spin & atom magnetic moments.
 On parallel- weak scattering
 On antiparallel-strong scattering
 More scattering= higher electrical reisitance

6. Why Nanoscale?
 Most scattering occurs at interface of ferromagnetic and
nonmagnetic layers.
 Electron mean free path (10-100nm) must be greater than
interlayer separation.
 Current-perpendicular-plane (CPP) more effective than
current-in-plane (CIP)—also more difficult to achieve.

7. Applications:
 The main application of GMR is magnetic field
sensors, which are used to read data in hard disk
drives, biosensors, microelectromechanical
systems (MEMS),spin value sensor, and other
devices.
 GMR multilayer structures are also used
in magnetoresistiverandom-access memory
(MRAM) as cells that store one bit of information.

8. Spin-Valve Senser
 Find magnetic field by measuring
electrical resistance.
Hard Drive &Mram.
 Information encoded in
magnetic domains.
 Reads heads sense
magnetic fields:
Relay information as
electrical signals.
 Before GMR ,hdd made of MRAM: Magnetic Ram low power
induction coils and OMR. consumption,fast speed.

9. Summary
 Up to 50% change in resistance under external
magnetic field.
 Nonmagnetic metal sandwiched between anti-
ferromagnetically coupled layers.
 Result of spin-dependent scattering, intrinsically
quantum effect.
 Huger impact on magnetic field sensors and hard
drives.

10. Any Question?