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11:11
Experimental Methods for Investigation of Shape Memory Based Elastocaloric Cooling Processes and Model Validation
Published on: May 2, 2016
Observation of a continuous phase transition in a shape-memory alloy
J C Lashley1, S M Shapiro, B L Winn
1Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Physical Review Letters
|October 15, 2008
Summary
Researchers studied AuZn and Au0.52Zn0.48 using various methods. They observed new magnetic Bragg peaks indicating a transition, with AuZn showing a continuous transition and a potential critical endpoint in its phase diagram.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Crystallography
Background:
- The study investigates the phase transitions in AuZn and Au0.52Zn0.48 alloys, materials known for complex structural behaviors.
- Understanding these transitions is crucial for developing novel electronic and magnetic materials.
Purpose of the Study:
- To characterize the nature of the phase transition in AuZn and Au0.52Zn0.48 using multiple experimental techniques.
- To investigate the influence of pressure on the transition temperature (TM) and identify potential critical points in the phase diagram.
Main Methods:
- Elastic neutron scattering to detect structural modulations via new Bragg peaks.
- Inelastic x-ray scattering to probe dynamic properties.
- Specific-heat measurements to identify thermodynamic signatures of the transition.
- Pressure-dependent electrical transport measurements to study the effect of pressure on TM.
Main Results:
- New commensurate Bragg peaks, indicative of a modulation, were observed in both AuZn and Au0.52Zn0.48 at their respective transition temperatures (TM).
- The transition was found to be continuous in AuZn, supported by the temperature dependence of Bragg peak intensity and specific-heat jump.
- A critical endpoint in the AuZn phase diagram was suggested, located at TM* = 2.7 K and p* = 3.1 GPa, based on pressure-dependent studies.
Conclusions:
- The study confirms the presence of a modulated phase in AuZn and Au0.52Zn0.48.
- AuZn exhibits a continuous phase transition, deviating from potentially discontinuous transitions in similar alloys.
- The identification of a critical endpoint provides new insights into the complex phase diagram of AuZn alloys.
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