Temperature Evolution of Magnon Propagation Length in Tm<sub>3</sub>Fe<sub>5</sub>O<sub>12</sub> Thin Films: Roles of Magnetic Anisotropy and Gilbert Damping
Amit Chanda, Christian Holzmann, Noah Schulz, Aladin Ullrich, Derick DeTellem, M. Albrecht, Miela Gross, Caroline A. Ross, Darío Arena, Manh‐Huong Phan, H. Srikanth
Abstract
The magnon propagation length, ⟨ξ⟩, of a ferro-/ferrimagnet (FM) is one of the key factors that controls the generation and propagation of thermally driven magnonic spin current in FM/heavy metal (HM) bilayer based spincaloritronic devices. For the development of a complete physical picture of thermally driven magnon transport in FM/HM bilayers over a wide temperature range, it is of utmost importance to understand the respective roles of temperature-dependent Gilbert damping (α) and effective magnetic anisotropy ( K eff ) in controlling the temperature evolution of ⟨ξ⟩. Here, we report a comprehensive investigation of the temperature-dependent longitudinal spin Seebeck effect (LSSE), radio frequency transverse susceptibility, and broad-band ferromagnetic resonance measurements on Tm 3 Fe 5 O 12 (TmIG)/Pt bilayers grown on different substrates. We observe a significant drop in the LSSE voltage below 200 K independent of TmIG film thickness and substrate choice. This is attributed to the noticeable increases in effective magnetic anisotropy field, H K eff (∝ K eff ) and α that occur within the same temperature range. From the TmIG thickness dependence of the LSSE voltage, we determined the temperature dependence of ⟨ξ⟩ and highlighted its correlation with the temperature-dependent H K eff and α in TmIG/Pt bilayers, which will be beneficial for the development of rare-earth iron garnet based efficient spincaloritronic nanodevices.