Reorientation of Spin Polarization in Pt via Elastic Spin Scattering for Efficient Magnetization Switching in Mn3Sn/Pt/Co Trilayer.

Spintronic devices driven by spin-orbit torque (SOT) technology hold immense potential for energy-efficient memory. Given the reliance of conventional SOT devices on magnetic fields, achieving field-free magnetization switching is a prerequisite for the advancement toward high-density integration. While harnessing low-symmetry materials enables switching without field via unconventional spin currents, however, this approach faces an intrinsic trade-off where the introduction of out-of-plane spin polarization compromises the dominant in-plane component, resulting in prohibitive critical current. Here, this study achieves the reconciliation of symmetry breaking and high driving efficiency of Pt through a solution based on a Mn3Sn/Pt/Co trilayer. Upon identifying Mn3.03Sn0.97 as the optimal composition through precise co-sputtering tuning, field-free switching with a ratio of 54% is demonstrated at a low critical current density of 3.86×106 A cm-2. Observing that a substantial decay and subsequent vanishing of the field-free switching ratio upon increasing Pt thickness or introducing insulating MgO barriers, accompanied by a reversal in switching polarity. This supports an elastic spin scattering mechanism where the non-collinear spin texture in Mn3Sn reorients Pt spin polarization. Crucially, this generates the out-of-plane component without sacrificing dominant in-plane polarization, enabling efficient field-free switching. This study highlights a scalable pathway for energy-efficient spintronic devices.