current-induced magnetization...
Post on 01-Mar-2019
218 Views
Preview:
TRANSCRIPT
Current-induced magnetization dynamics
Pavel Baláž
Institute of Molecular Physics, Polish Academy of Sciences, Poznan, PolandAdam Mickiewicz University, Faculty of Physics, Division of Mesoscopic Physics, Poznan, Poland
FINS Initiative Symposium, 6-th June 2014, NTNU Trondheim
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 1 / 17
1 About me
2 Introduction to spintronics
3 Current-induced magnetization dynamics
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 2 / 17
About me
Outline
1 About me
2 Introduction to spintronics
3 Current-induced magnetization dynamics
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 3 / 17
About me
Few words about me...
1983 Born in Slovakia
2006 Graduated in Physics at P. J. Šafárik University in Košice, Slovakia
2007-2010 Early stage researcher at Marie Currie Research Training Network
SPINSWITCH at A. Mickiewicz University in Poznan, Poland
2012 PhD in Physics
Now Postdoc at Polish-Swiss Research Project NANOSPIN
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 4 / 17
Spintronics
Outline
1 About me
2 Introduction to spintronics
3 Current-induced magnetization dynamics
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 5 / 17
Spintronics
Spintronics: spin electronics
electron
energy
charge
Conventional electronics
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 6 / 17
Spintronics
Spintronics: spin electronics
electron
energy
charge
spin
spin + electronics =Spintronics
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 6 / 17
Spintronics
Electrons in a metal
Nonmagnetic material
each spin has different direction
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 7 / 17
Spintronics
Electrons in a metal
Magnetic material
~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M~M
electrons polarize their spins: N↑ > N↓
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 7 / 17
Spintronics
Spin injection into nonmagnet
Current polarization
Ferromagnet Nonmagnet
electric current
js ∝ e−x/λ
x
spin current persists also in a nonmagnet for a long distance
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 8 / 17
Spintronics
Spin valves and Giant magnetoresistance
spin
spin
Nobel Prize in Physics in 2007
M. N. Baibich, J. M. Broto, A. Fert, F. Nguyen Van Dau, F. Petroff, P. Etienne, G. Creuzet, A. Friederich, and J. Chazelas
Giant Magnetoresistance of (001)Fe/(001)Cr Magnetic Superlattices
Phys. Rev. Lett. 61, 2472–2475 (1988)
G. Binasch, P. Grünberg, F. Saurenbach, and W. Zinn
Enhanced magnetoresistance in layered magnetic structures with antiferromagnetic interlayer exchange
Phys. Rev. B 39, 4828–4830 (1989)
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 9 / 17
Dynamics
Outline
1 About me
2 Introduction to spintronics
3 Current-induced magnetization dynamics
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 10 / 17
Dynamics
Spin transfer torque
J. C. Slonczewski
Current-driven excitation of magnetic multilayers
J. Magn. Magn. Mater. 159, L1-L7 (1996)
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 11 / 17
Dynamics
Spin transfer torque
J. Barnas, A. Fert, M. Gmitra, I. Weymann, V.K. Dugaev
From giant magnetoresistance to current-induced switching by spin transfer
Phys. Rev. B 72, 024426 (2005)
Spin-transfer torque
τ =h
2(j⊥L − j⊥R)
τ‖ = a(θ ) I m× (m×M)
τ⊥ = b(θ ) I m×M
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 11 / 17
Dynamics
Advantages and disadvantages
Advantages
Current-induced switching isfaster then the one induced bymagnetic field
Possibility of higher density ofmagnetic elements
nonvolatile
Open problems
too high current densities arerequired
high Joule heating
energy consuming
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 12 / 17
Dynamics
Dual spin valves
P. Baláž, M. Gmitra, J. Barnas
Current-induced dynamics in noncollinear dual spin valves
Phys. Rev. B 80, 174404 (2009)
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 13 / 17
Dynamics
Dual spin valves
higher spin torque
Spin transfer torque
P. Baláž, M. Gmitra, J. Barnas
Current-induced dynamics in noncollinear dual spin valves
Phys. Rev. B 80, 174404 (2009)
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 13 / 17
Dynamics
Dual spin valves
higher spin torque
faster switching
reduced critical current density
Switching time
P. Baláž, M. Gmitra, J. Barnas
Current-induced dynamics in noncollinear dual spin valves
Phys. Rev. B 80, 174404 (2009)
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 13 / 17
Dynamics
Dual spin valves
higher spin torque
faster switching
reduced critical current density
smaller magnetoresistance
P. Baláž, M. Gmitra, J. Barnas
Current-induced dynamics in noncollinear dual spin valves
Phys. Rev. B 80, 174404 (2009)
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 13 / 17
Dynamics
Perpendicular polarizer
PP FL
reduced critical current
lack of initial ringing
strongly dependent on current pulse
problem with measurement ofmagnetoresistance
A. D. Kent, B. Ozyilmaz, E. del Braco
Spin-transfer-induced precessional magnetization reversalAppl. Phys. Lett. 84, 3897 (2004)
O. J. Lee et al.
Ultrafast switching of a nanomagnet by a combined out-of-plane andin-plane polarized spin current pulse
Appl. Phys. Lett. 95, 125067 (2009)
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 14 / 17
Dynamics
Dual spin valves with perpendicular polarizer
PP FL IPNL NR
low critical current density
Switching probability
P. Baláž, M. Zwierzycki, J. Barnas
Spin-transfer torque and current-induced switching in metallic spin valves with perpendicular polarizersPhys. Rev. B 88, 094422 (2013)
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 15 / 17
Dynamics
Dual spin valves with perpendicular polarizer
PP FL IPNL NR
low critical current density
ultrafast switching undersubnanosecond current pulse
Switching probability
P. Baláž, M. Zwierzycki, J. Barnas
Spin-transfer torque and current-induced switching in metallic spin valves with perpendicular polarizersPhys. Rev. B 88, 094422 (2013)
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 15 / 17
Dynamics
Dual spin valves with perpendicular polarizer
PP FL IPNL NR
low critical current density
ultrafast switching undersubnanosecond current pulse
reliable switching even at roomtemperature
Switching probability
P. Baláž, M. Zwierzycki, J. Barnas
Spin-transfer torque and current-induced switching in metallic spin valves with perpendicular polarizersPhys. Rev. B 88, 094422 (2013)
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 15 / 17
Dynamics
Dual spin valves with perpendicular polarizer
PP FL IPNL NR
low critical current density
ultrafast switching undersubnanosecond current pulse
reliable switching even at roomtemperature
reasonable magnetoresistance
Switching probability
P. Baláž, M. Zwierzycki, J. Barnas
Spin-transfer torque and current-induced switching in metallic spin valves with perpendicular polarizersPhys. Rev. B 88, 094422 (2013)
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 15 / 17
Summary
Summary and perspectives
Spintronics is a promising way towards faster and more efficient memory drivesand computers
Further improvements are necessary
spin valve design and subtle switching schemes
utilizing of novel materials (not only metals)
making use of various aspects of solid state physics (semiconductors,superconductivity, spin-orbit coupling,...)
P. Baláž (Poznan, Poland) Magnetization dynamics FINS Initiative Symposium 16 / 17
www.nanospin.agh.edu.pl
Thank you for your attention!
www.ifmpan.poznan.pl www.zfmezo.amu.edu.pl
top related