Spin-charge coupling in lightly doped Nd2-xCexCuO4 -: art. no. 054505

We use neutron scattering to study the influence of a magnetic field on spin structures of Nd2CuO4. On cooling from room temperature, Nd2CuO4 goes through a series of antiferromagnetic (AF) phase transitions with different noncollinear spin structures. While a c-axis aligned magnetic field does not alter the basic zero-field noncollinear spin structures, a field parallel to the CuO2 Plane can transform the noncollinear structure to a collinear one (spin-flop transition), induce magnetic disorder along the c axis, and cause hysteresis in the AF phase transitions. By comparing these results directly to the magnetoresistance (MR) measurements of Nd1.975Ce0.025CuO4, which has essentially the same AF structures as Nd2CuO4, we find that a magnetic-field-induced spin-flop transition, AF phase hysteresis, and spin c-axis disorder all affect the transport properties of the material. Our results thus provide direct evidence for the existence of a strong spin-charge coupling in electron-doped copper oxides.