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| Home > Publications database > Elucidating barocaloric effect in spin crossover compounds with inelastic scattering methods |
| Talk (non-conference) (Invited) | FZJ-2025-04283 |
2025
Abstract: The barocaloric effect (BCE) is characterized as a thermal response (variation of temperature or entropy) 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 (LS) and high spin (HS) states can be switched by hydrostatic pressure, were proposed as a potential mechanism to generate outstanding BCE. In this work, we aim to unveil the correlation between structure change and dynamic properties of a classic SCO complex Fe(PM-BiA)2(NCS)2 (with PM = N-2’- pyridylmethylene and BiA = 4-aminobiphenyl) for elucidating the impact of cooperativity on the barocaloric performance.Fe(PM-BiA)2(NCS)2 crystallizes in two different structures (orthorhombic (OP) with abrupt transition and monoclinic (MP) with gradual transition). The complete and Fe-related density of states are accessed through inelastic neutron scattering (INS) and nuclear inelastic scattering (NIS), respectively. The single crystal diffraction evidences the potential dynamic disorder of phenyl groups. A two-site reorientation mode of the phenyl group at the picosecond time scale has been realized by quasi elastic neutron scattering (QENS). Furthermore, through a combination of complementary inelastic scattering techniques, we quantitatively unveiled the microscopic origin of the giant entropy change, providing direct experimental insight into its underlying mechanism. Our study deepens the understanding of caloric effects in SCO complexes and promotes their potential application as BCE refrigerants.
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