Magneto-Optical Detection of Spin-Orbit Torques

Spin-orbit torques (SOTs) are of great importance for the efficient manipulation of magnetization in spintronic devices. They enable fast, energy-efficient magnetization control and provide several advantages over spin-transfer torques, including simplified device geometries with optical access to the magnetic free layer, scalability, and compatibility with semiconductor technologies. Quantifying SOT efficiencies and distinguishing between different torque symmetries are central issues in this rapidly developing field. Although a variety of experimental techniques have been used, including spin-torque ferromagnetic resonance, spin pumping, and harmonic Hall measurements, establishing a microscopic understanding of the origins of the torques and separating symmetry contributions remains challenging. 

In this talk, I will discuss a new magneto-optic Kerr Sagnac interferometer developed at NYU that enables optical detection of spin-orbit torques with nanoradian sensitivity. The instrument enables highly sensitive, diffraction-limited, symmetry-resolved studies of SOTs in magnetic heterostructures and two-dimensional materials. I will present our initial results quantifying SOTs in ferrimagnetic heterostructures, as well as benchmark measurements on conventional Permalloy/Pt and CoFeB/Pt bilayers. 

* Work on ferrimagnetic heterostructures was done in collaboration with Akilan K, Sébastien Petit- Watelot, Melissa Yactayo, Laurent Badie, Stéphane Mangin, Michel Hehn, and Juan-Carlos Rojas- Sánchez. 

Séminaire organisé dans le cadre du programme interdisciplinaire MAT-PULSE (Materials and Physics @ Ultimate Scale: Nanotech for a sustainable digital world)