Thermodynamic and neutron diffraction studies on multiferroic NdMn sub(2)O sub(5)

Magnetically frustrated RMn sub(2)O sub(5) oxides have attracted considerable attention in recent years, because most of the members of this family show spin ordering induced dielectric polarization along with strong magneto-electric coupling. Although the true origin of the ferroelectricity is still a matter of debate, it has been observed that the magneto-electric phase diagram can be substantially tuned with the variation of rare earth elements. In this work, we have chosen NdMn sub(2)O sub(5) as the compound of our interest since it lies exactly in between the ferroelectric and non-ferroelectric members of this family and also, because there are few investigations performed on RMn sub(2)O sub(5) systems with large rare earth atoms. With the combination of heat capacity, magnetic susceptibility, dielectric permittivity, powder X-ray diffraction, and powder neutron diffraction measurements, it has been found that NdMn sub(2)O sub(5) undergoes an incommensurate magnetic ordering around 30 K followed by a possible ferroelectric-like transition at ~26 K. Another lock-in kind of magnetic transition appears when the temperature is decreased to ~15 K. With further lowering of temperature, an antiferromagnetic ordering, which is presumably associated with the Nd super(3+), is achieved near 4 K. This study thus sheds light on a new compound of the RMn sub(2)O sub(5) series presenting different multiferroic properties.