Observing soft x-ray magnetization-induced second harmonic generation at a heterojunction interface

Abstract

Second harmonic generation (SHG) spectroscopy in the visible and infrared regions has been a useful tool to selectively probe electronic properties at surfaces and interfaces. By examining variation of SHG under a magnetic field, one can also evaluate magnetic properties at the surfaces/interfaces. When multiple elements are involved in SHG, however, it is difficult to separate their contributions. In order to meet the demand of studying increasingly complex magnetic multilayer materials, element selectivity is desired. Here, using an Fe-based multilayer sample with broken inversion symmetry, we present observation of magnetization-induced SHG in the soft x-ray regime around the Fe M-shell absorption edge. Significant variation of SHG signal was captured depending on the direction of the magnetic moment, assuring sensitivity of the measurement likely enhanced by the Fe M-edge inner-shell resonance. The present methodology paves the way for element specific studies of magnetic properties at buried interfaces.