Bimagnon studies in cuprates with resonant inelastic x-ray scattering at the O K edge. II. Doping effect in La2-xSrxCuO4

We present RIXS data at the O K edge from La2-xSrxCuO4 vs doping between x = 0.10 and x = 0.22 with attention to the magnetic excitations in the mid-infrared region. The sampling done by RIXS is the same as in the undoped cuprates provided the excitation is at the first prepeak induced by doping. Note that this excitation energy is about 1.5 eV lower than that needed to see bimagnons in the parent compound. This approach allows the study of the upper region of the bimagnon continuum around 450 meV within about one third of the Brillouin zone around Gamma. The results show the presence of damped bimagnons and of higher even order spin excitations with almost constant spectral weight at all the dopings explored here. The implications for high-T-c studies are briefly addressed.