WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
Nat Commun. 2017 Jun 12;8:15859. doi: 10.1038/ncomms15859.
To know the properties of a particle or a wave, one should measure how its energy changes with its momentum. The relation between them is called the dispersion relation, which encodes essential information of the kinetics. In a magnet, the wave motion of atomic spins serves as an elementary excitation, called a spin wave, and behaves like a fictitious particle. Although the dispersion relation of spin waves governs many of the magnetic properties, observation of their entire dispersion is one of the challenges today. Spin waves whose dispersion is dominated by magnetostatic interaction are called pure-magnetostatic waves, which are still missing despite of their practical importance. Here, we report observation of the band dispersion relation of pure-magnetostatic waves by developing a table-top all-optical spectroscopy named spin-wave tomography. The result unmasks characteristics of pure-magnetostatic waves. We also demonstrate time-resolved measurements, which reveal coherent energy transfer between spin waves and lattice vibrations.
为了了解粒子或波的性质，人们应该测量其能量随动量的变化。它们之间的关系称为色散关系，它包含了动力学的重要信息。在磁体中，原子自旋的波运动充当基本激发，称为自旋波，并表现得像虚拟粒子。尽管自旋波的色散关系支配着许多磁性性质，但观察它们的整个色散关系是当今的一个挑战。色散关系主要由静磁相互作用支配的自旋波称为纯静磁波，尽管它们具有实际重要性，但仍未被观察到。在这里，我们通过开发一种名为自旋波层析成像的桌面全光学光谱学方法，报告了纯静磁波的能带色散关系的观察结果。该结果揭示了纯静磁波的特征。我们还演示了时间分辨测量，揭示了自旋波和晶格振动之间的相干能量转移。
