High resolution neutron scattering study of low‐energy magnetic excitations in Nd_2‐<i>x</i>Ce_<i>x</i>CuO₄

Abstract

Abstract The low‐energy magnetic excitations ( ħ ω ≤ 2 meV) of polycrystalline samples of Nd 2‐ x Ce x CuO 4 with x = 0, 0.1 and 0.15 have been measured with high resolution inelastic neutron scattering using time‐of‐flight technique at temperatures below 0.3 K. All observed scattering originates from transitions within the ground state doublet of Nd 3+ . For Nd 2 CuO 4 the response is inelastic, and shows at least three different modes, of which one is almost dispersionless. For x = 0.1 the excitation spectrum shifts towards lower energies, but the main features of the undoped compound are still visible, whereas for x = 0.15 the response is mainly quasi‐elastic but remains localised in Q‐space around the first magnetic Bragg point (0.5 0.5 1). A comparison with data obtained on a triple‐axis‐spectrometer on single crystals with x = 0.0 and x = 0.15 reveals that the response of the doped sample in the [0 0 1] direction is still inelastic.