Enhanced magnon transport through an amorphous magnetic insulator

Magnonics research is focused on the transport of spin information via spin-wave, or magnon, excitations. Due to its exceptionally low damping, the magnetic insulator Yttrium Iron Garnet (YIG) is considered the most prominent material in this field. New research has been stimulated by a report of long (µm) magnon diffusion lengths in amorphous YIG (a-YIG) where there is no long range magnetic order. Similar experiments have failed to reproduce the results and spin-pumping data provides a much lower (3.6nm) spin diffusion length. We have recently measured a 28nm spin diffusion length in a-YIG (28nm) and hypothesise that samples of a-YIG may differ depending on growth conditions. In this proposal we will use polarized neutron reflectometry to investigate a-YIG in order to see if deviations away from the expected M = 0 emu/cc can explain the longer spin diffusion length in our samples.

磁子学（Magnonics）研究的核心方向是通过自旋波（spin-wave）或磁子（magnon）激发实现自旋信息的传输。作为一类磁性绝缘体，钇铁石榴石（Yttrium Iron Garnet, YIG）因具备极低的阻尼特性，被视作该领域最具代表性的材料。此前有研究报道称，在无长程磁有序的非晶态钇铁石榴石（amorphous YIG, a-YIG）中存在微米级的磁子扩散长度，这一发现推动了该领域的多项新研究。但后续同类实验均未能复现该结果，且自旋泵浦（spin-pumping）实验数据显示，其测得的自旋扩散长度仅为3.6纳米，远短于前述报道的数值。我们近期在非晶态钇铁石榴石样品中测得的自旋扩散长度为28纳米，并据此提出假设：非晶态钇铁石榴石样品的特性可能因生长条件的不同而存在差异。在本研究提案中，我们将采用极化中子反射谱（polarized neutron reflectometry）对非晶态钇铁石榴石开展表征，以验证：若样品的磁化强度偏离预期的0 emu/cc，是否能够解释我们所观测到的更长自旋扩散长度。