Reorientation of Spin Polarization in Pt via Elastic Spin Scattering for Efficient Magnetization Switching in Mn 3 Sn/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 Mn 3 Sn/Pt/Co trilayer. Upon identifying Mn 3.03 Sn 0.97 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 3.86×10 6 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 Mn 3 Sn 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.