Metamagnetic transition in Y2Cu2O5

Neutron diffraction experiment has been performed to determine the magnetic structures in magnetic fields up to 6 T on a single crystal of Y2Cu2O5 which shows strange metamagnetic transitions at Hc1 = 3.0 T and Hc2 = 4.8 T for H parallel b. At H = 0, the determined magnetic structure is identical with that obtained for the powder sample, but new diffraction peaks appear at completely unexpected positions between Hc1 and Hc2, which means a three-lattice period modulation along the b-axis but this structure change is mysterious from the crystallographic point of view. (orig.)