Bryan Chávez University of South Carolina, Physics and...
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Bryan Chávez University of South Carolina, Physics and Astronomy
Graduate Seminar October 31, 2014
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Introduction to 2007s Physics Nobel
Early Years
Giant Magnetoresistances (GMR)
Spintronics
Applications
Conclusion
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Awarded: "for the discovery of Giant Magnetoresistance”
Awarded to: Albert Fert and Peter Grünberg
Actually discovery was in 1988
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Spin waves experiments were done by Peter Grünberg
Done through Raman Light Scattering
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Form of Raman scattering
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Looked at how an electron
moves through a magnetic
multilayer
The two magnetic layers
are Fe(~20nm) with
Cr(~1nm) in between them
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M M
M M Current
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First theoretical theory for Giant Magnetoresistance
Based on Boltzmann distribution
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M M
current
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Original experiment had the current in plane with the multilayer
Spintronics is based off of current perpendicular to plane of multilayer
current current
Current Perpendicular to Plane
Current In Plane 11
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Giant Magnetoresistance lead to spintronics
Moved away from dealing with charge to spin
Conventional circuit analysis deals with bulk charge through current
Spintronics attempts to manipulate the spin of an electron
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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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r
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Similar to Light Polarization
J. Slonczewski, JMMM 1996, L. Berger, PR B 1996
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Current perpendicular to plane effect with an insulator instead of conductor
Can be used as switches or to store data
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Magnetic Sensors
Tunneling Switches
Magnetic Random Access Memory
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Currently used in hard drives and lead to the ability to make 1 terabyte drives
Used to measure small magnetic fields
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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 Tesla = fridge magnet
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Uses the tunnel junction to store data in a matrix
Possibly to replace all current forms of memory storage- “universal memory”
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Ferromagnetic semiconductors
Spin transfer oscillators
Phone gaussmeters
Traffic control sensors
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Giant Magnetoresistance has changed the way electronics are thought about
Giant Magnetoresistance has lead to great advances in our understanding of the manipulation of electron spins
Spintronics is wide open to many new advances to help us in computing
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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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