Large spin-mixing conductance in Bi-doped Cu/YIG interfaces

Trabajo presentado en la 9th Joint European Magnetic Symposia Conference, celebrada en Mainz (Alemania) del 3 al 7 de septiembre de 2018In the field of spintronics, the Spin Hall Effect provides an efficient tool for the conversion of a charge current into a spin current without the need of ferromagnets [1]. Recently, a Spin Hall Angle of 0.25 has been measured in Cu doped with 0.25% Bi [2] and larger values of are expected for larger Bi doping according to theoretical calculations [3]. In this work we incorporate up to 10% of Bi atoms into the Cu structure without evidence of Bi surface segregation of cluster formation, as studied by several microscopic and spectroscopic techniques. We investigate the spin pumping effect in a series of yttrium-iron-garnet (YIG)–Cu(Bi) bilayers by the measurement of broadband ferromagnetic resonance (FMR). We determine the effective spin-mixing conductance as a function of Bi concentration by comparing the FMR response of pure YIG layers and Cu(Bi)/YIG bilayers in a frequency range from 2-10 GHz. With a Cu(Bi) layer on top of the YIG the Hilbert damping is significantly enhanced (up to 40%). The effective spin-mixing conductance extracted from the ferromagnetic resonance experiments increase with the Bi concentrations up to a value of Geff = 7.3x1018 m2 . [1] J. Sinova et al. Rev. Mod. Phys. 87, 1213 (2015) [2] Y. Niimi et al. Phys. Rev. Lett. 109, 156606 (2012) [3] B. Gu, et al. J. Appl. Phys. 117, 17D503, (2015).Peer reviewe