Determination of Intrinsic Ferroelectric Polarization in Orthorhombic Manganites with E-type Spin Order

TL;DR

This study accurately measures the intrinsic ferroelectric polarization in orthorhombic RMnO3 compounds with E-type spin order, revealing how polarization varies with rare earth ions and correlates with structural parameters.

Contribution

It provides direct measurements of remanent ferroelectric polarization in orthorhombic RMnO3, highlighting the dominant role of Mn t2g orbitals and the influence of ionic size on polarization.

Findings

LuMnO3 has the largest Pr of 0.17 μC/cm^2 at 6 K.

Pr decreases with increasing rare earth ion radius from Lu to Ho.

Polarization correlates with Mn-O-Mn bond angles and Mn-O distances.

Abstract

By directly measuring electrical hysteresis loops using the Positive-Up Negative-Down (PUND) method, we accurately determined the remanent ferroelectric polarization Pr of orthorhombic RMnO3 (R = Ho, Tm, Yb, and Lu) compounds below their E-type spin ordering temperatures. We found that LuMnO3 has the largest Pr of 0.17 uC/cm^2 at 6 K in the series, indicating that its single-crystal form can produce a Pr of at least 0.6 \muuC/cm^2 at 0 K. Furthermore, at a fixed temperature, Pr decreases systematically with increasing rare earth ion radius from R = Lu to Ho, exhibiting a strong correlation with the variations in the in-plane Mn-O-Mn bond angle and Mn-O distances. Our experimental results suggest that the contribution of the Mn t2g orbitals dominates the ferroelectric polarization.