current-induced magnetization...

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


About me

Outline

1 About me




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


Spintronics

Outline

1 About me




Spintronics

Spintronics: spin electronics

electron

energy

charge

Conventional electronics


Spintronics

Spintronics: spin electronics

electron

energy

charge

spin

spin + electronics =Spintronics


Spintronics

Electrons in a metal

Nonmagnetic material

each spin has different direction


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↓


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


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)


Dynamics

Outline

1 About me




Dynamics

Spin transfer torque

J. C. Slonczewski

Current-driven excitation of magnetic multilayers

J. Magn. Magn. Mater. 159, L1-L7 (1996)


Dynamics


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


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


Dynamics

Dual spin valves

P. Baláž, M. Gmitra, J. Barnas

Current-induced dynamics in noncollinear dual spin valves

Phys. Rev. B 80, 174404 (2009)


Dynamics

Dual spin valves

higher spin torque




Phys. Rev. B 80, 174404 (2009)


Dynamics

Dual spin valves

higher spin torque

faster switching

reduced critical current density

Switching time



Phys. Rev. B 80, 174404 (2009)


Dynamics

Dual spin valves

higher spin torque

faster switching

reduced critical current density

smaller magnetoresistance



Phys. Rev. B 80, 174404 (2009)


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)


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)


Dynamics


PP FL IPNL NR


ultrafast switching undersubnanosecond current pulse





Dynamics


PP FL IPNL NR



reliable switching even at roomtemperature





Dynamics


PP FL IPNL NR



reliable switching even at roomtemperature

reasonable magnetoresistance





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,...)


www.nanospin.agh.edu.pl

Thank you for your attention!

www.ifmpan.poznan.pl www.zfmezo.amu.edu.pl

current-induced magnetization...

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