Impact of ultrathin garnet spacers on the magnetotransport in Tb3Fe5O12/Pt bilayers

We studied the interfacial spin Hall magnetotransport in the Tb3Fe5O12 (TbIG)/Pt system across a non-magnetic [Y3Al5O12 (YAG) and Gd3Ga5O12 (GGG)] spacer with garnet structure. TbIG (30 nm)/spacer samples were grown on single-crystal (GGG) (111) substrates by pulsed laser deposition before 5 nm of Pt was sputtered on the samples and patterned into Hall bars. The YAG spacer thickness (t(YAG)) dependences of anomalous Hall effect resistance (R-AHE) indicated no significant change on the magnetization compensation temperature of TbIG. Hysteretic R-AHE loops were observed at low magnetic fields, but with reducing magnitude as t(YAG) thickness increases. A crossover of the R-AHE sign was observed at temperatures below the compensation temperature, which decreased sharply from 135 to 34 K as t(YAG) increased from 0 to 1 nm. We attributed this to the strong dependence of the magnetic proximity effect toward the YAG insertion in the TbIG/Pt interface. Replacement of the YAG spacer with GGG showed significant impact on the R-AHE behavior. No obvious R-AHE-H loops were observed in the TbIG/Pt sample inserted with 0.5 nm GGG spacer, which could be linked to the strong magnetic contribution of the Gd ions. This work highlights the tunability of interfacial transport behavior in iron garnet/heavy metal systems through ultrathin spacers, providing guidance for the interfacial design of spintronic devices.