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PhysicsCoral Gables, Florida 33124, USA
The Spin BatteryStewart E. Barnes
Physics
Stewart E. Barnes
Spin
battery
Spin Battery
S. E. Barnes and S. Maekawa Phys. Rev. Lett. 98 246601 (2007)
Physics
Stewart E. Barnes
Except for solar cells, the generation of electrical power invariably corresponds to the conversion of mechanical into electric energy. The basic physical principle involved is Faraday's law of induction. On the other hand, in a battery, energy is invariably stored in chemical form. When needed, energy is produced via reversible chemical reactions. Charging the battery runs the reaction in the opposite direction. An electrical current corresponds to a flow of electrons and in both, Faraday law generation and chemical storage, it is the electrical charge of an electron which is important.
Physics
Stewart E. Barnes
Faraday’s Law
Michael Faraday
Physics
Stewart E. Barnes
Faraday’s Law
Michael Faraday
Physics
Stewart E. Barnes
Physics
Stewart E. Barnes
Physics
Stewart E. Barnes
Spintronics is a relatively new field and is the art of creating new electronic devices which use the other attribute of an electron, namely its “spin”. The current trust in this area is the development of STT-MRAM (spin-torque-transfer magnetic-random-access-memory). An electron in addition to having an elementary charge -e also constitutes a small magnetic dipole which corresponds to its “spin”. It is essentially this property of an electron which is responsible for the magnetism of all magnet materials starting with elemental magnets such as Ni or Fe. In a typical spintronics device electrons pass from one thin film magnet to another through a thin oxide barrier. The spin-torque-transfer process reverses the direction of the magnetisation of one of these magnetic layers. If the layer in one direction is “0” this writes a “1” into memory.
Physics
Stewart E. Barnes
Charge current in
Charge current out
Free layerSmallanisotropyenergy
Fixed layerLargeanisotropyenergy
ferromagnetConduction electron polarisation p
Basics:
Polarisation of charge current:
Physics
Stewart E. Barnes
Hideo OHNO
Hitachi-Tohoku Univ. Jointly Prototype 2 Mbit Nonvolatile RAM Based on Spin Torque Transfer
Physics
Stewart E. Barnes
Vector additions
Physics
Stewart E. Barnes
Ralph-Stiles
Physics
Stewart E. Barnes
Single-Electronics – Made Easy
Single-electronics implies the possibility to control the movement and position of a single electron or a small number of electrons. It is interesting to see how strong an influence a single electron with the minute charge of 1.6·10-19C C. Consider an uncharged small metallic sphere with a radius of 1 nm, something quite possible being produced today.
Coulomb Blockade
Fig. 1: An electron approaching a small uncharged metallic sphere will feel a small attractive force caused by its own image charge in the sphere. Once the sphere is charged by a single electron, following electrons will feel a strong repelling Coulomb force.
Physics
Stewart E. Barnes
Physics
Stewart E. Barnes
Nano-magnets
Physics
Stewart E. Barnes
Physics
Stewart E. Barnes
Which direction is the current?
The Kondo surface.
Physics
Stewart E. Barnes
Spin
battery
Spin Battery
S. E. Barnes and S. Maekawa Phys. Rev. Lett. 98 246601 (2007)
Physics
Stewart E. Barnes
Working magnetic material
Energy
Parameter
High energy state
Low energy state
Electrical energy
Spin Faraday - STT - process
Physics
SU(2) gauge theory, the Berry phase and spintronics, TCM Cambridge, June 12 2008Stewart E. Barnes
A single domain wall
S. E. Barnes and S. Maekawa Phys. Rev. Lett. 98 246601 (2007)
Geoffrey S. D. Beach
S. A. Yang, G. S. D. Beach, C. Knutson, D. Xiao, Q. Niu, M. Tsoi,and J. L. Erskine, Phys. Rev. Lett. 102, 067201 (2009).
Physics
SU(2) gauge theory, the Berry phase and spintronics, TCM Cambridge, June 12 2008Stewart E. Barnes
Physics
Stewart E. Barnes
Spin battery
A tale of many channels
Physics
Stewart E. Barnes
Physics
Stewart E. Barnes
Physics
Stewart E. Barnes
Working magnetic material
Energy
Parameter
High energy state
Low energy state
Electrical energy
Spin Faraday - STT - process
Physics
Stewart E. Barnes
Physics
Stewart E. Barnes
Physics
Stewart E. Barnes
Physics
Stewart E. Barnes
104 J/kg - conservative105 J/kg - optimistic
4.6 X105 J/kg - Li - ion
Physics
Stewart E. Barnes
Theoretical Maximum
If one changes the magnetic state it is possible to recover the Jsd~4eV exchange energy.
This gives 4.0x106 J/kg
Physics
Stewart E. Barnes
Direction:
1. Confirm emf for different nano-magnet system.
2. Vary parameters to check theory.
3. Develop theory and experiment for new materials.
4. Address the “scale up’’ possibilities.
5. Demonstration batteries.
Develop theory for present and new devices.
Physics
Stewart E. Barnes
Hideo OHNO
Hitachi-Tohoku Univ. Jointly Prototype 2 Mbit Nonvolatile RAM Based on Spin Torque Transfer
Physics
Stewart E. Barnes
Physics
Stewart E. Barnes
Physics
Stewart E. Barnes
- - -
+ + +Es
Physics
Stewart E. Barnes
+- - - - - -
+ + + + + +
Es Es
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Stewart E. Barnes
+- - - - - -
+ + + + + +
Es Es
Physics
Stewart E. Barnes
+- - - - - -
+ + + + + +
Es Es
Physics
Stewart E. Barnes
“Inverse blockade”
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Stewart E. Barnes
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Stewart E. Barnes
Physics
Stewart E. Barnes
Physics
Stewart E. Barnes
Magnetic behaviour
Physics
Stewart E. Barnes
Physics
Stewart E. Barnes
