Temperature and Pressure-driven Spin transitions and Piezochromism in a Mn-based Hybrid Perovskite

TL;DR

This study reveals that a hybrid perovskite, DMAMnF, exhibits temperature and pressure-driven spin transitions and piezochromism, with potential applications in memory, display, and switching devices due to its near-room-temperature transition and accessible pressure range.

Contribution

The paper demonstrates for the first time that DMAMnF shows controllable spin transitions and piezochromism driven by external stimuli, combining first-principles calculations with experimental relevance.

Findings

Spin transition from low to high spin state occurs near room temperature.

Hysteresis in spin transition driven by elastic interactions and magnetic superexchange.

Spin transition is coupled with piezochromic behavior.

Abstract

Hybrid perovskites have been at the forefront of condensed matter research particularly in context of device applications primarily in relation to applications in the field of solar cells. In this article, we demonstrate that several new functionalities may be added to the arsenal of hybrid perovskites, in terms of external stimuli driven spin transitions as well as piezochromism. As an example, we study Dimethylammonium Manganese Formate (DMAMnF), a hybrid perovskite investigated quite extensively experimentally. We show by employing first principles DFT+U calculations with the aid of ab initio molecular dynamics calculations that DMAMnF shows temperature and pressure driven spin transitions, from a low spin $S=1/2$ to a high spin $S=5/2$ state. This transition is accompanied by a hysteresis, and we find that this hysteresis and the transition temperature are quite close to room temperature, which is desirable for device applications particularly in memory, display, and switching devices. The operating pressure is a few GPa, which is accessible in standard laboratory settings. We find that the cooperative behaviour showing up as hysteresis accompanying the transition is driven primarily by elastic interactions, assisted by magnetic superexchange between Mn atoms. Last but not least we demonstrate that the spin transition is associated with piezochromism which could also be important for applications.