TY  - CONF
AU  - Qi, J.
AU  - Prakash, P.
AU  - Schwärzer, K.
AU  - Shahed, H.
AU  - Allgaier, Jürgen
AU  - Perßon, J.
AU  - Sergeev, I.
AU  - Glazyrin, K.
AU  - Rols, S.
AU  - De Souza, N.
AU  - Yu, D.
AU  - Grzechnik, A.
AU  - Angst, M.
AU  - Voigt, J.
AU  - Friese, K.
AU  - Sohn, Y.
AU  - Prajapat, D.
TI  - Elucidating entropy contributions of barocaloric effect in spin crossover complex Fe(PM-BiA)2(NCS)2
M1  - FZJ-2025-02979
PY  - 2025
AB  - Background: The barocaloric effect (BCE) is characterized as a thermal response in solid-state materials induced by external hydrostatic pressure. Cooling technologies based on the BCE have emerged as a promising alternative to conventional vapor-compression cooling. Recently, spin crossover (SCO) transitions, where the low spin and high spin states can be switched by hydrostatic pressure, were proposed as a potential mechanism to generate outstanding BCE. Fe(PM-BiA)2(NCS)2 (with PM = N-2’- pyridylmethylene and BiA = 4-aminobiphenyl) is a classic SCO complex that crystalizes in two different structures, orthorhombic with abrupt transition and monoclinic with gradual transition. In this work, we aim to unveil the entropy contributions of Fe(PM-BiA)2(NCS)2 for optimizing the BCE performance on SCO complexes. Methods: Spectroscopic methods including nuclear inelastic scattering (NIS, P01), inelastic neutron scattering (INS, PANTHER & PELICAN) and quasi elastic scattering (QENS, PANTHER & EMU) have been used for dynamic studies of Fe(PM-BiA)2(NCS)2. Results: The dynamic features of both polymorphs over a large energy range are highlighted by spectroscopic methods. The complete and Fe-related lattice dynamics have been accessed through INS and NIS, respectively. It indicates that the Fe-related entropy change across the spin transition is around 54.6% of the total entropy change. The single crystal X-ray diffraction evidences the potential dynamic disorder of phenyl groups. A two-site reorientation mode of the phenyl group at the ps time scale has been observed by QENS. This local mode also generates 12% of the total entropy change.Conclusion: In summary, we confirm that both the phonon excitations of Fe-N octahedron and the local motions of phenyl groups play crucial roles in contributing to the total entropy change in Fe(PM-BiA)2(NCS)2. Our study will enhance the understanding of the caloric effect in the SCO complex and promote the application of SCO complexes as BCE refrigerants.
T2  - The International Conference on Neutron Scattering
CY  - 6 Jul 2025 - 10 Jul 2025, Bella Center in Copenhagen, Denmark, with the last day at the European Spallation Source (ESS) in nearby Lund, Sweden (Denmark)
Y2  - 6 Jul 2025 - 10 Jul 2025
M2  - Bella Center in Copenhagen, Denmark, with the last day at the European Spallation Source (ESS) in nearby Lund, Sweden, Denmark
LB  - PUB:(DE-HGF)24
UR  - https://juser.fz-juelich.de/record/1043681
ER  -