High-quality single-crystal thulium iron garnet films with perpendicular magnetic anisotropy by off-axis sputtering

Abstract

High-quality single-crystal thulium iron garnet (TmIG) films of 10-30 nm thick were grown by off-axis sputtering at room temperature (RT) followed by post-annealing. X-ray photoelectron spectroscopy (XPS) was employed to determine the TmIG film composition to optimize the growth conditions, along with the aid of x-ray diffraction (XRD) structural analysis and atomic force microscope (AFM) for surface morphology. The optimized films exhibited perpendicular magnetic anisotropy (PMA) and the saturation magnetization at RT was ∼99 emu/cm3, close to the RT bulk value ∼110 emu/cm3 with a very low coercive field of ∼2.4 Oe. We extracted the H⊥ of 1734 Oe and the peak-to-peak linewidth ΔH of ferromagnetic resonance are only about 99 Oe, significantly lower than that of PLD grown TmIG film and bulk single crystals. The high-quality sputtered single-crystal TmIG films show great potential to be integrated with topological insulators or heavy metals with strong spin-orbit coupling for spintronic applications.

High-quality thulium iron garnet films with tunable perpendicular magnetic anisotropy by off-axis sputtering – correlation between magnetic properties and film strain

“…Out-of-plane lattice constants of samples A, B, C and E were 12.274 Å, 12.289 Å, 12.299 Å and 12.302 Å, respectively. The gradual increase of the out-of-plane lattice constant reflected a Tm-richer composition as L increased, consistent with the previous composition investigation 13 . The Tm: Fe ratio of samples are determined by Rutherford backscattering spectrometry (RBS) and X-ray photoelectron spectroscopy (XPS) in the Supplementary information S1.…”

“…Figure 1 shows the structural and magnetic properties of the optimized off-axis sputtered TmIG thin film on GGG(111) with a longitudinal distance of 7 cm 13 . The cross-sectional TEM image and the energy-dispersive X-ray spectroscopy (EDS) element mapping images shown in Fig.…”

“…However, the small deposition area is the major shortcoming of PLD, limiting its application in industry. As an alternative way to deposit oxide thin films, we have successfully utilized off-axis magnetron sputtering to grow high-quality TmIG films with excellent crystallinity and PMA on GGG(111) 13 and observed a negative magnetoresistance in TI/TmIG hetero-structures, revealing time-reversal symmetry breaking in TI 14 . The advantage of off-axis sputtering includes fewer ion bombardments and applications of large-scale growth.…”

Magnetism and spin transport in rare-earth-rich epitaxial terbium and europium iron garnet films

“…The RE:Fe ratio exceeds 0.6 in both cases, with values of 0.72 for EuIG (001) and 0.70 for TbIG. This iron deficiency is consistent with similar XPS analyses of sputtered TmIG films and PLD-grown YIG films, which showed Y:Fe ratios as large as 1.37 [27,33].…”

“…Other thin film RE garnets include GdIG (Gd 3 Fe 5 O 12 ) [25] and LuIG (Lu 3 Fe 5 O 12 ) [26] with in plane easy axis. Out of the PMA RE garnets, TmIG is the most extensively studied in terms of the spintronic properties of the FMI/HM interface [19,[27][28][29][30]. TmIG/HM devices exhibited SOT-driven reversal with applied fields as low as 2 Oe and evidence of fast current-induced domain wall velocities reaching 1000 m/s at a current density of 2.5 × 10 12 A/m 2 in the Pt [28].…”