Microscopic View of the Magnon Spin Current―Observation of Magnon Polarization

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Other Title
  • 絶縁体におけるスピン流伝播の微視的機構――マグノン極性の観測
  • ゼツエンタイ ニ オケル スピンリュウ デンパ ノ ビシテキ キコウ : マグノン キョクセイ ノ カンソク

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Abstract

<p>Spin current, a flow of the spin degree of freedom in condensed matter, is a fundamental concept in spintronics research. Many experimental and theoretical investigations are devoted to developing creation/annihilation and control methods of the spin current. Deep into microscopic views, the spin current in magnetic insulators is carried by the transverse component of spin-waves (quantized magnons). Magnons can be polarized, and the magnon polarization, i.e., the direction of the precessional motion of the electronic spin, affects the thermodynamics of magnetic materials, governing the magnitude and sign of the spin current. However, the magnon polarization of magnon modes has eluded experimental observation. We measure the mode-resolved magnon polarization of the quintessential magnet Y3Fe5O12 (YIG), through the chiral term detection of inelastic polarized neutron scattering. There exist major two magnon modes, and the gap separating optical and acoustic modes is of the order of the thermal energy at room temperature. A maximum of the observed spin current near room temperature has been interpreted in terms of the competition between magnon modes with opposite polarization. Our experimental findings are well accounted for by atomistic spin dynamics calculations of the scattering cross section.</p>

Journal

  • Butsuri

    Butsuri 76 (4), 214-219, 2021-04-05

    The Physical Society of Japan

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