J. Herrero-Martín, A. N. Dobrynin, C. Mazzoli, P. Steadman, P. Bencok, R. Fan, A. A. Mukhin, V. Skumryev, and J. L. García-Muñoz. Phys. Rev. B 91, 220403(R)
Doping Mn1−xCoxWO4 with Co produces a rich magnetic phase diagram with a large number of ferroelectric phases. We present resonant x-ray magnetic scattering experiments in the known collinear AF4 phase of multiferroic Mn0.85Co0.15WO4 showing that Mn and Co spins point to different directions despite they randomly occupy the same crystallographic site. The resultant noncollinear exotic spin configuration is determined by a competition of Mn2+ and Co2+ magnetic anisotropies and demands a reexamination of the ferroelectric phase diagram of this model family beyond the previous average description of its magnetic orders.