Spin waves in La₂CuO₄ investigated by neutrons using diffraction method

High-temperature superconductivity in cupric oxides, which are derived from parent antiferromagnetic Mott insulator oxides such as La₂CuO₄ (LCO), continues to attract significant attention, despite decades of intensive research. Neutron scattering studies of magnetic structures and excitations have provided valuable insight into the interplay between magnetism, electronic dynamics, and superconductivity in these materials. In the parent compound LCO, the in-plane magnetic interactions have been extensively characterized via spin-waves measurements with neutrons; however, important questions remain, particularly regarding the spin-wave gap and interlayer interactions. Characterization of these parameters are limited by the fact that the spin-wave signal in cuprates is weak and full measurement of magnetic excitation spectrum on a neutron spectrometer is very time-consuming. As a result, the interlayer dispersion is usually integrated over to improve the signal. A thorough understanding of these magnetic properties in LCO and their evolution with doping in the derived superconductor family is important because they are intertwined with charge stripe arrangement in the doped compounds and with position and dynamics of the apical oxygens, which play important roles in superconductivity. Here, we report spin-wave measurements in LCO using diffraction method, which we recently reinvented. This method employs a neutron diffractometer equipped with a large, highly pixelated area-sensitive detector without energy analysis and provides a significant increase in throughput, enabling the exploration of the spin-wave gap and interlayer dispersion in LCO.