Lattice dynamics of KAgF3 perovskite, unique 1D antiferromagnet

TL;DR

This study combines DFT calculations and experimental Raman measurements to analyze the vibrational properties of KAgF3, revealing detailed phonon modes and a phase transition that does not significantly alter vibrational spectra.

Contribution

It provides a comprehensive vibrational mode assignment for KAgF3 using advanced computational methods and experimental validation, highlighting the nature of its phase transition.

Findings

Good correlation between calculated and experimental vibrational modes (R2>0.997)

Identification of 12 vibrational bands as IR or Raman active

Phase transition at 230 K is an order-disorder type with minimal impact on vibrational structure

Abstract

Theoretical DFT calculations using GGA+U and HSE06 frameworks enabled vibrational mode assignment and partial (atomic) phonon DOS determination in KAgF3 perovskite, a low-dimensional magnetic fluoroargentate(II). Twelve bands in the spectra of KAgF3 were assigned to either IR active or Raman active modes, reaching very good correlation with experimental values (R2>0.997). Low-temperature Raman measurements indicate that the intriguing spin-Peierls-like phase transition at 230 K is an order-disorder transition and it does not strongly impact the vibrational structure of the material.