MnCaTa2O7-A Magnetically Ordered Polar Phase Prepared via Cation Exchange

Subhadip Mallick; Fabio Orlandi; Pascal Manuel; Weiguo Zhang; P Shiv Halasyamani; Michael A Hayward

doi:10.1021/acs.chemmater.3c01850

MnCaTa₂O₇-A Magnetically Ordered Polar Phase Prepared via Cation Exchange

Chem Mater. 2023 Sep 9;35(18):7839-7846. doi: 10.1021/acs.chemmater.3c01850. eCollection 2023 Sep 26.

Authors

Subhadip Mallick¹, Fabio Orlandi², Pascal Manuel², Weiguo Zhang³, P Shiv Halasyamani³, Michael A Hayward¹

Affiliations

¹ Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, UK.
² ISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxon OX11 0QX, UK.
³ Department of Chemistry, University of Houston, 112 Fleming Building, Houston, Texas 77204-5003, United States.

Abstract

Reaction between the pseudo-Ruddlesden-Popper phase Li₂CaTa₂O₇ and MnCl₂ at 375 °C yields MnCaTa₂O₇, a paramagnetic polar phase (space group P2₁nm), which adopts an a^-b^-c⁺/b^-a^-c⁺ distorted, layered perovskite structure. Magnetization and neutron diffraction data show that MnCaTa₂O₇ adopts an antiferromagnetically ordered state below T_N = 56 K and exhibits large lattice parameter anomalies and a transient increase in its polar distortion mode at T_A = 50 K. However, in contrast to the related phase MnSrTa₂O₇, MnCaTa₂O₇ shows no strong signature of weak ferromagnetism and thus shows no signs of magnetoelectric coupling. The differences in physical behavior between the two MnATa₂O₇ phases appear to be related to their differing Mn cation-order and differing TaO₆ tilting schemes and demonstrate that even subtle changes to these orderings can have large effects on the distortion-mode couplings, which drive complex behavior of this class of "hybrid improper" ferroelectric material.