Nonlinear Optical Studies of Neel Order and Spin Domains in Antiferromagnetic MnN

Antiferromagnetic (AF) materials has been drawing increasing attention for practical applications due to their ultrafast spin dynamics. θ-MnN, a metallic AF, exhibits many properties that are interesting for spin switching applications such as a low anisotropy field and a high Neel temperature (650 K) [1]. A challenge in studying spin domains, and their switching, in AF materials is the lack of readily available experimental techniques that can be used to determine the orientation of the Neel vector. In this work, we use optical second harmonic generation to study the Neel order and spin domains in single-crystal epitaxially-grown MnN. Our results show that spins in θ-MnN are ferromagnetically aligned in planes perpendicular to the c-axis and have a large out-of-plane tilt which results in 2/m1’ magnetic point group. Different spin domains correspond to the in-plane component of the spins aligned along the two in-plane crystal cubic axes. Our measurements reveal that the sizes of the spin domains are smaller than a micron. We will also present results from nonlinear optical imaging of spin switching in MnN/Pt devices in which spin orbit torque is used to switch the Neel vector. [1] Phys. Rev. Research 2, 013347 (2020).