Giant Spin-Charge Conversion in Ultrathin Films of the MnPtSb Half-Heusler Compound

Half-metallic half-Heusler compounds with strong spin-orbit-coupling and broken inversion symmetry in their crystal structure are promising materials for generating and absorbing spin-currents, thus enabling the electric manipulation of magnetization in energy-efficient spintronic devices. In this work, the spin-to-charge conversion in the sputtered half-Heusler MnPtSb within thickness (t) range from 1 to 6 nm is reported. A combination of X-ray and transmission electron microscopy measurements evidence the epitaxial nature of these ultrathin non-centrosymmetric layers, with a clear (111)-orientation on top of (0001) single-crystal sapphire. By broadband ferromagnetic resonance (FMR), a four orders of magnitude tunable spin accumulation in the MnPtSb-based heterostructures, within t = 1–6 nm range, is observed. By using spin pumping FMR, a remarkable t-dependent spin-charge conversion in the MnPtSb layers is measured, which clearly demonstrates the interfacial origin of the conversion. When interpreted within the inverse Edelstein effect (IEE), the spin-charge conversion efficiency extracted at room temperature for the thinnest MnPtSb layer reaches λIEE≈3 nm, representing an extremely high conversion. The still never explored ultrathin regime of the MnPtSb films studied in this work and the discovery of their outstanding functionality are two ingredients that demonstrate the potentiality of such materials for future applications in spintronics.