Exploring spin-phonon coupling, barocaloric, and polar phonon features in the multiferroic [(CH₃)₂NH₂][Mn(N₃)₃]...

We report a temperature-dependent Raman scattering study of the hybrid organic-inorganic azide perovskite of formula [(CH₃)₂NH₂][Mn(N₃)₃]([DMA][Mn(N₃)₃]). The Raman spectra reveal distinct shifts in phonon frequencies, particularly in the ν_sCNC and ν_s(ν₁)N₃^- modes, demonstrating that spin-phonon interactions play a critical role in their thermal and magnetic responses. Differential scanning calorimetry confirmed a first-order structural phase transition, from an orthorhombic high-temperature HT(α) phase, belonging to the Cmca space group, to a monoclinic low-temperature LT(β) phase, with P2₁ symmetry. The associated entropy change was found to be |∆S| ∼ 8.45 J mol^-1 K^-1 (37.2 J kg^-1 K^-1), and the barocaloric (BC) coefficient (|δTt/δP|) was ∼2.94 K kbar^-1, estimated by using the Clausius-Clapeyron method. Room-temperature FTIR reflectivity spectra revealed the polar phonon modes and their corresponding damping coefficients, showing minimal contributions from the DMA⁺ cation to the intrinsic dielectric constant (∼4.3). These results provide new insights into the coupling between lattice dynamics, spin interactions, and barocaloric behavior in azide-based hybrid perovskites.