Neutron-diffraction studies of YMnO 3

We have made thermal expansion and neutron- diffraction studies of YMnO3, and found that our bulk meas- urements showed anomalous behavior at TN = 80 K. The an- alysis of the neutron-diffraction data shows that the magnetic scattering of YMnO3 can be described equally well by the Γ1 and Γ3 representations of space group P63cm. Around the Ntemperature, we also find that the lattice constants change anomalously, implying the existence of a magneto- electric effect.