Magnetic ground state of low-doped manganites probed by spin dynamics under magnetic field

Abstract We present a neutron scattering study of spin dynamics under magnetic field in La 0.9 Ca 0.1 MnO 3 . In zero field, the spin wave spectrum consists of two branches, a high and a low-energy one. In applied field, the high-energy branch splits into two branches due to twinned domains. The gap of the new intermediate-energy branch strongly decreases above a spin-flop transition that occurs for H // b and H >2 T. Furthermore, this branch, that we could attribute to the twinned domain H // b , shows a q -discontinuity under field. The low-energy branch, measurable only around ferromagnetic zone centers at H =0, appears at all q -values under field.