We use transport and neutron-scattering measurements to show that a magnetic-field-induced transition from noncollinear to collinear spin arrangement in adjacent ${\mathrm{CuO}}_2$ planes of lightly electron-doped ${\mathrm{Pr}}_{1.3-x}{\mathrm{La}}_{0.7}{\mathrm{Ce}}_x{\mathrm{CuO}}_4$ ($x=0.01$) crystals affects significantly both the in-plane and out-of-plane resistivity. In the high-field collinear state, the magnetoresistance (MR) does not saturate but exhibits an intriguing fourfold-symmetric angular dependence, oscillating from being positive at $\mathbf{B}\Vert [100]$ to being negative at $\mathbf{B}\Vert [110]$. The observed MR of more than 30% at low temperatures induced by a modest modification of the spin structure indicates an unexpectedly strong spin-charge coupling in electron-doped cuprates.

• Received 20 October 2003

DOI:https://doi.org/10.1103/PhysRevLett.92.227003