About this Abstract |
Meeting |
2026 TMS Annual Meeting & Exhibition
|
Symposium
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Thermodynamics and Kinetics of Alloys IV
|
Presentation Title |
Pressure-Induced Invar Behavior in Ferromagnetic Materials |
Author(s) |
Brent Fultz, Elena Priesen-Reis, Anne Lin |
On-Site Speaker (Planned) |
Brent Fultz |
Abstract Scope |
The classic Invar effect, where thermal expansion is near zero, occurs in Fe-36Ni at ambient pressure and temperature. In 2001, it was reported that Invar behavior in Fe-45Ni occurs under pressure, but this pressure-induced Invar effect was considered exotic. We use diffraction and nuclear spectroscopies with synchrotron radiation to measure lattice parameters, phonon spectra, and magnetization of samples under pressure in diamond-anvil cells. From these data, the entropies of spins and phonons are obtained under pressure, and assessed with a Maxwell relationship: ∂S/∂P = –∂V/∂T. The ∂V/∂T is the thermal expansion. The contributions to thermal expansion from spins and phonons under pressure are found to cancel precisely at specific pressures below the Curie pressures of Fe-45Ni and Fe-32Pd (approx. 8 and 6 GPa) where Invar behavior is seen in X-ray diffraction. We argue that pressure-induced Invar effects should be commonplace in ferromagnets. Supported by NSF Grant 1904714. |
Proceedings Inclusion? |
Planned: |
Keywords |
Phase Transformations, Characterization, |