MnCaTa₂O₇-A Magnetically Ordered Polar Phase Prepared via Cation Exchange.

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.

SUBMITTER: Mallick S 

PROVIDER: S-EPMC10538500 | biostudies-literature | 2023 Sep

REPOSITORIES: biostudies-literature