Symmetry breaking and spin lattice coupling in $NdCrTiO_{5}$

The origin of multiferroicity in NdCrTiO5 has been examined. A first-order phase transition, due to breakingof the inversion symmetry, near the low-temperature antiferromagnetic ordering (TN ∼ 21 K) where spontaneouselectric polarization also appears, is confirmed. From synchrotron x-ray powder diffraction measurements, thestructure at low temperatures is found to be noncentrosymmetric (space group Pba2), justifying the polarbehavior of this compound below TN . Temperature-dependent Raman measurements reveal that the lattice isstrongly coupled with the spins, pointing to the spin lattice correlations in a noncentrosymmetric space groupbeing responsible for invoking the ferroelectricity below 21 K. Through time-of-flight neutron powder diffractionexperiments, it is confirmed that the magnetic sublattices, both Nd and Cr, simultaneously order at TN , and at temperaturesbelow 15 K the Cr moments are found to be saturated while the Nd moments continue to grow until 6 K