Crystal and magnetic structures of the oxyphosphates MFePO5 (M = Fe, Co, Ni, Cu). Analysis of the magnetic ground state in terms of superexchange interactions
N. El Khayati, R. Cherkaoui El Moursli, J. Rodríguez-Carvajal, G. André, N. Blanchard, F. Bourée, G. Collin and T. Roisnel