Magnetic And Electric Properties In The Distorted Tetrahedral Spin Chain System Cu3mo2o9

We study the multiferroic properties in the distorted tetrahedral quasi-one dimensional spin system Cu3Mo2O9, in which the effects of the low dimensionality and the magnetic frustration are expected to appear simultaneously. We clarify that the antiferromagnetic order is formed together with ferroelectric properties at T-N = 7.9 K under zero magnetic field and obtain the magnetic-field-temperature phase diagram by measuring dielectric constant and spontaneous electric polarization. It is found that the antiferromagnetic phase possesses a spontaneous electric polarization parallel to the c axis when the magnetic field H is applied parallel to the a axis. On the other hand, there are three different ferroelectric phases in the antiferromagnetic phase for H parallel to the c axis.