CrO4 distortion-driven ferroelectric order in (R,Y)CrO4(<

Abstract

We report a new multiferroic family of (R,Y)CrO 4 (R = Sm, Gd, and Ho). The ferroelectric ordering temperatures are observed at much higher temperatures than their corresponding magnetic ordering temperatures for all the members. The values of electric polarization (P) are significantly high, which vary from ∼217 to ∼640 μC/m 2 for a 4 kV/cm poling field. The large value of P (∼590 μC/m 2) for YCrO 4 compared to the smallest P value in the series for GdCrO 4 signifies that the magnetic rare-earth element does not directly influence the P value. Our careful analysis of the low-temperature synchrotron diffraction studies confirms that the distortion of CrO 4 tetrahedra directs the P value. The structural transformation from the centrosymmetric I 4 1 /amd structure to a noncentrosymmetric I42d space group at the onset of polar order is found to be correlated with the appearance of spontaneous electric polarization.

High-temperature ferroelectric order and magnetoelectric coupling driven by the magnetic field cooling effect in R2BaCuO5(R=Er,Dy,Sm)<

“…Our micro-structural studies indicate that the distortions of CuO 5 polyhedra involve the rotations, which lead to a key role for the ferroelectric order. This is analogous to that observed for RCrO 3 [41,42] and RCrO 4 [36].…”

“…This signature around T FE in the integrated intensity plot is correlated with the change in the scattering cross section and may point to a possible structural transition. The change in the integrated intensity is similar to that observed for the reported ferroelectric materials, where ferroelectricity appeared due to structural transition [26,[36][37][38]. With further decreasing temperature a sharp fall is observed around T N1 , as depicted in Fig.…”

“…For Er 2 BaNiO 5 a short-range order driven ferroelectricity was proposed, whereas a structural transition to a noncentrosymmetric polar structure has been proposed for the occurrence of ferroelectricity in the case of Sm 2 BaNiO 5 . Similar results with a much higher T FE than the magnetic order was observed for RCrO 4 (R = Sm, Gd, and Ho) series, which was proposed to be correlated with the structural transition to a nonpolar structure [36]. Herein, the structural transition to a polar structure of Pna2 1 space group is proposed at T FE from the noncentrosymmetric Pnma space group.…”

Natural ferroelectric order near ambient temperature in the orthoferrite HoFeO3

“…The absence of signature in the high temperature may be attributed to the overlapping of the intrinsic component with the extrinsic components such as the grain boundary and the sample-electrode interface effects. [34][35][36] Appearance of a ferroelectric order is first detected along the c-axis from the pyroelectric current measurements, while the sample is cooled from different poling temperatures (T pole ), as shown in Fig. S1 of the supplemental information (SI) 37 .…”

Symmetry breaking and spin lattice coupling in NdCrTiO5

“…The relative intensity of these reflections suddenly decreases below ∼20 K, marking a clearcut structural transition around this temperature. Changes in the integrated diffraction intensities have been widely used as a tool to show a structural transition [19,20].…”