Spin-flop transition and the anisotropic magnetoresistance of Pr(1.3-x)La(0.7)CexCuO4: unexpectedly strong spin-charge coupling in the electron-doped cuprates

We use transport and neutron-scattering measurements to show that a magnetic-field-induced transition from noncollinear to collinear spin arrangement in adjacent CuO2 planes of lightly electron-doped Pr(1.3-x)La(0.7)CexCuO4 (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 B//[100] to being negative at B//[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.