Three Jahn-Teller states of matter in the spin-crossover system Mn(taa)

TL;DR

This paper identifies three distinct phases in the Mn(taa) spin-crossover system, including a Jahn-Teller liquid phase, using first-principles calculations and Monte Carlo simulations, revealing complex phase behavior and interactions.

Contribution

It introduces the concept of a Jahn-Teller liquid phase in spin-crossover materials, highlighting the role of impurity mixing and strain interactions in phase transitions.

Findings

Discovery of three phases: solid, liquid, and gas in Mn(taa)

Jahn-Teller liquid arises from impurity mixing and strain interactions

Strain interactions influence phase transition and magnetoelectric coupling

Abstract

Three high-spin phases recently discovered in the spin-crossover system Mn(taa) are identified through analysis by a combination of first-principles calculations and Monte Carlo simulation as a low-temperature Jahn-Teller ordered (solid) phase, an intermediate-temperature dynamically correlated (liquid) phase, and an uncorrelated (gas) phase. In particular, the Jahn-Teller liquid phase arises from competition between mixing with low-spin impurities, which drive the disorder, and inter-molecular strain interactions. The latter are a key factor in both the spin-crossover phase transition and the magnetoelectric coupling. Jahn-Teller liquids may exist in other spin-crossover materials and materials that have multiple equivalent Jahn-Teller axes.