Direct measurement of the two components of the spin-orbit-torque (SOT) in NiFe/Pt bilayers by an AMR-based Wheatstone bridge (Conference Presentation)

We will present an alternative method for spin-torque measurements and spin-currents interface characterization in a pure DC configuration measurement. It consists in consists in developing an home-made NiFe-based 4-branches AMR Wheatstone bridge sensors with a specific design allowing opposite spin-current flow in each of the opposite bridge arms. We have experimented the method on well-characterized NiFe(10nm)/Pt as well as NiFe(10nm)/Pt/Au:W systems reliable for spin-torque and THz emission. If the field-like torque and Oersted field simply manifest by a shift in the characteristic transfer of the sensors, the antidamping torque is generally more subtle to evidence. We will present the characteristics of the developed sensors in terms of sensitivity and angular resolution below 0.05°. We will present in details the specific method and protocol measurements in the out-of-plane field geometry allowing from specific symmetry considerations the extraction of the antidamping component, linear in the current density and with a magnitude of 10 G for a current density of 3x1011 A.cm-2. The amplitude of the spin-torque measured is in close agreement with the expectations [7] and with models including spin-memory loss effects like recently revealed by spin-pumping FMR experiments [4]. References: [1] I.M. Miron et al., Nat Mater. 9, 230 [2010]. [2] Frances Hellman et al., Rev. Mod. Phys. 89, 025006 [2010]. [3] J.-C. Rojas-Sanchez et al., Phys. Rev. Lett. 112, 106602 [2014]. [4] A. J. Berger et al., Phys. Rev. B 98, 024402 [2018]. [5] L. Liu et al., Phys. Rev. Lett. 106, 036601 [2011]. [6] K. Garello et al., Nat.Nano. 8, 587 (2013)[7] T. Seifert et al., Nat. Phot. 10, pages 483–488 [2016].