Hiroyuki Inoue Electric manipulation of spin relaxation in a film using spin-Hall effect K. Ando et al (PRL in press)

Why Spintronics? A Relativistic View

Relativity says Duality of Electricity and Magnetism E ↔ B P ↔ M

P P’ M’ v

M P’ M’ v

N S P V v (j c ) Ｍ Wilson’s experiment (1913) rotating magnetization Inducing electromotiveforce (EMF) (electric polarization P)

electricity → electric charge ρ e electric current → charge current J c magnetism → magnetic charge (dipole) ρ m magnetic dipole current → spin current J s Harness the duality of Electricity and Magnetism E, P charge B, M spin Fundamental Purposes of Spintronics

Introduction of Spin Current opens a New Perspective to Magnetic Phenomena

A Wise Saying (!?) by Yehoshua Ah? What is spin current? Why do we need to think about spin current? OK, then, I will go to a market. and I will buy a banana current! Spin current is not that stupid thing to think about…

xx μ↑μ↑ μ↓μ↓ J↑J↑ J↓J↓ Current of Electrons in Solids up-spin currentdown-spin current

Electric Current & Spin Current = = chargespin J c = J ↑ + J ↓ J s = J ↑ - J ↓ Charge Current Spin Current e σ v v charge current and spin current

H eff M -M×H D Magnetization damping term Dissipation of angular momentum Transferred to conduction electrons Generation of spin current (μ ↑ ≠ μ ↓ ) Magnetization Relaxation = Production of Spin Current Phenomenological Description of Magnetization Dynamics Landau-Lifshitz-Gilbert equation

H eff M -M×H eff D Balance of emission and absorption of angular momentum Ferromagnetic Resonance Ferromagnetic Resonance = Continuous Generation of Spin Current EM Supply angular momentum by EMW Continuous operation of spin pumping Maintain magnetization-precession Driving Magnetization Precession Generates Spin Current σ v

Experiments

-e JSJS JcJc JcJc JSJS Spin-Hall effectInverse spin-Hall effect 1. Zhang et al. PRL (2000) 2. Murakami et al. science (2003) 3. Sinova et al. PRL (2004) 4. Kimura et al. JMMM (2004) 5. Kato et al. science (2004) 6. Wunderlich et al. PRL (2005) 7. Ueda et al. APL(2006) intrinsic: Band Berry Phase extrinsic: Impurity Scattering Spin Hall Effect Spin-Orbit interaction (relativistic effect)

Ni 81 Fe 19 (10 nm)(FM) Pt (10 nm)(NM) SiO 2 substrate E MW TE 011 microwave cavity H V,I Sweep & Lock-in H MW derivative of Lorentzian function Experimental Setup

μ↑μ↑ μ↓μ↓ J↑J↑ J↓J↓ Ni 81 Fe 19 Pt Enhancement of M relaxation Pt layer Enhances Relaxation of Magnetization

10 -3 V/T EMF due to ISHE ( J s → J c ) = ( M → P ) Lorentz transformation in a solid H. Inoue, K. Ando et al. (J. Appl. Phys) Spin Current Injection Indeed Yields EMF -e JcJc JSJS

Inverse Process Realizes Electrical Manipulation of M-relaxation I Spin-Hall effect: spin current injection to Ni 81 Fe 19 layer spin torque manipulates the damping term δM⊥δM⊥ M D spin torque ( J c → J s ) = ( P → M )

direction of current: direction of polarization of spin current current intensity: amount of spin torque modulation of M-relaxation asscociated with the current-directional reversal

electrical manipulation of magnetization relaxation this scheme is applicable for spin-current meter conventionally, difficult to achieve after once material species, temperature, and pressure are given

They realized electric manipulation of magnetization relaxation, which can be also applied to spin-current meter. Spin current introduces new perspectives to magnetic phenomena which harness the duality of electricity and magnetism. Main Points to Remember

magnetic monopoles can exist in solids… S N S

θθ’θ’ j si ≈∂ i θj ssi ≈M×∂ i M superconductorferromagnet MM’ Super charge currentSuper spin current Josephson Effect of Charge and Spin

A Deduction of Super Spin Current

Charge density Super Spin Current Spin Continuity Equation Electric current Charge Continuity Equation Deduction of Super Spin Current