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Bryan Chávez University of South Carolina, Physics and Astronomy Graduate Seminar September 19, 2014 1

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Page 1: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

Bryan ChávezUniversity of South Carolina, Physics and Astronomy

Graduate SeminarSeptember 19, 2014

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Page 2: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

Introduction to 2007s Physics Nobel Early Years Giant Magnetoresistances (GMR) Spintronics Applications Conclusion

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Page 3: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

Awarded: "for the discovery of Giant Magnetoresistance”

Awarded to: Albert Fert and Peter Grünberg Actually discovery was in 1988

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Page 4: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

Spin wave experiments done by Peter Grünberg

Done through Raman Light Scattering

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Page 5: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

Look at how an electronmoves through a magneticmultilayer The two magnetic layersare Fe(~12nm) with Cr(~1nm) in between

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Page 6: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

First Theoretical theory for Giant Magnetoresistance

Based on Boltzmann’s diffusion equation

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Page 7: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

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Page 8: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

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Page 9: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

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Page 10: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

Original experiment had the current in plane with the multilayer

Spintronics is based off of current perpendicular to plane of multilayer

currentcurrent

Current Perpendicular to Plane

Current In Plane10

Page 11: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

Giant Magnetoresistance leads to spintronics Moved away from dealing with charge to deal

with electron spin Conventional circuit analysis deals with bulk

charge through current Spintronics attempts to manipulate the spin

of an electron

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Page 12: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

The barrier between the Fe and the spacer causes an accumulation of spins

If you have an anti-parallel B field on the other side it produces a torque

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Page 13: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

Similar to Light Polarization

J. Slonczewski, JMMM 1996, L. Berger, PR B 199613

Page 14: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

Current Perpendicular to Plane effect with an insulator instead of conductor

Can be used as switches or to store data

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Page 15: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

Magnetic Sensors Tunneling Switches Magnetic Random Access Memory

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Page 16: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

Currently used on hard drives and lead to the ability to make 1 terabyte drives

Used to measuring small magnetic fields

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Page 17: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

Tunnel junctions can be used as switches or to store data

To switch a junction the B field needs to be ~100 Oe = 0.01 Telsa = fridge magnet

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Page 18: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

Uses the Tunnel junction to store data in a matrix

Possibly to replace all current forms of memory storage

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Page 19: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

Ferromagnetic semiconductors Spin transfer oscillators Phone gaussmeters Traffic control sensors

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Page 20: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

Giant Magnetoresistance has change the way electronics are thought about

Giant Magnetoresistance has lead to great advance in out understand of the manipulation of electron spins

Spintronics is wide open to many new advance to help us in computing

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Page 21: Bryan Chávez University of South Carolina, Physics and ...boson.physics.sc.edu/~gothe/730-F14/talks/bryan-1.pdf · Bryan Chávez University of South Carolina, Physics and Astronomy

Fert, Albert. The Origin, devolopment and future of spintronics. 2007.Grünberg, Peter. From spinwaves to Giant Magnetoresistance (GMR)

and beyond. 2007.Rodgers, Peter. Nanoscience And Technology : A Collection Of Reviews

From Nature Journals. Singapore: World Scientific, 2010. eBook Collection (EBSCOhost). Web. 18 Sept. 2014.

Xia, Jianbai, Kai Chang, and Weikun Ge. Semiconductor Spintronics. Singapore: World Scientific, 2012. eBook Collection (EBSCOhost). Web. 18 Sept. 2014.

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