Bryan Chávez University of South Carolina, Physics and Astronomy

Graduate Seminar October 31, 2014

1

Introduction to 2007s Physics Nobel

Early Years

Giant Magnetoresistances (GMR)

Spintronics

Applications

Conclusion

2

Awarded: "for the discovery of Giant Magnetoresistance”

Awarded to: Albert Fert and Peter Grünberg

Actually discovery was in 1988

3

Spin waves experiments were done by Peter Grünberg

Done through Raman Light Scattering

4

Form of Raman scattering

5

Looked at how an electron

moves through a magnetic

multilayer

The two magnetic layers

are Fe(~20nm) with

Cr(~1nm) in between them

6

M M

M M Current

First theoretical theory for Giant Magnetoresistance

Based on Boltzmann distribution

7

M M

current

8

9

10

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

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

12

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

13

r

Similar to Light Polarization

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

14

Current perpendicular to plane effect with an insulator instead of conductor

Can be used as switches or to store data

15

Magnetic Sensors

Tunneling Switches

Magnetic Random Access Memory

16

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

Used to measure small magnetic fields

17

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

18

Uses the tunnel junction to store data in a matrix

Possibly to replace all current forms of memory storage- “universal memory”

19

Ferromagnetic semiconductors

Spin transfer oscillators

Phone gaussmeters

Traffic control sensors

20

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

21

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.

22