Giant magnetoresistance

Giant magnetoresistance.iiui.

1. Giant magnetoresistance 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 Fer t

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?