  We report NdCrTiO5 to be an unusual multiferroic material with large magnetic
field dependent electric polarization. While magneto-electric coupling in this
two magnetic sub-lattice oxide is well established, the purpose of this study
is to look for spontaneous symmetry breaking at the magnetic transition. The
conclusions are based on extensive magnetization, dielectric and polarization
measurements around its antiferromagnetic ordering temperature of 18K. Room
temperature X-ray diffraction pattern of NdCrTiO5 reveals that the sample is
single phase with an orthorhombic crystal structure that allows linear
magneto-electric coupling. DC magnetization measurement shows magnetization
downturn at 11K together with a small kink corresponding to the Co+3
sub-lattice ordering at ~18K. An anomaly in dielectric constant is observed
around the magnetic ordering temperature that increases substantially with
increasing magnetic field. Through detailed pyroelectric current measurements
at zero magnetic field, particularly as a function of thermal cycling, we
establish that NdCrTiO5 is a genuine multiferroic material that is possibly
driven by collinear magneto-striction.
