The momentum space distribution of the low-energy magnetic response in Nd1.85Ce0.15CuO4 at T <= 0.1 K and up to 5.7 T

The momentum space distribution of the magnetic response of Nd3+ spins in a single crystal of Nd1.85Ce0.15CuO4 has been measured with inelastic neutro n scattering as a function of an applied magnetic field along [0 1 0]. The observed q-widths along [1 0 0] and [0 0 1] of the tetragonal lattice are r ather large in the low-field region up to 2T, which corresponds to the heav y-fermion phase. A drastic decrease in q-width occurs to higher fields. The q-width of the magnetic response at (0 0 2) along the [1 0 0] direction ch anges by a factor two, while in the [0 0 1] direction and around (0 0 3) th e decrease is 30% to 40%. Nevertheless, all observed q-widths remain signif icantly broadened up to 5.7T. (C) 2000 Elsevier Science B.V. All rights res erved.