Crystal structure and compressibility of FePt nanoparticles under high pressures and high temperatures

Abstract

FePt nanoparticles with an average grain size of 4 nm and equiatomic composition of Fe and Pt was studied under high pressures in a diamond anvil cell to investigate its structural stability and compressibility under high compression. The ambient pressure disordered face-centered-cubic (fcc) phase was found to be stable to the highest pressure of 61 GPa (compression of 15%) at room temperature. The compression of Fe₅₀Pt₅₀ nanoparticles is closer to the compression curve for pure Pt and shows lower compressibility than what would be expected for a bulk Fe₅₀Pt₅₀ alloy. The nanoparticle character of Fe₅₀Pt₅₀ sample is maintained to the highest pressure without any observable grain coarsening effects at ambient temperature. Laser heating of disordered fcc phase at 32 GPa to a temperature of 2000 K resulted in a phase transformation to a microcrystalline phase with the distorted fcc structure.

Keywords:

• Nanoparticles
• Iron–Platinum alloys
• Phase transformations
• Compressibility

Acknowledgements

We acknowledge support form the Division of Materials Research-Metals Program, National Science Foundation (NSF) under Grant No. DMR-0203779. This research was conducted (in part) at the National Synchrotron Light Source, Brookhaven National laboratory, which is supported by the US Department of Energy, Division of Material Sciences and Division of Chemical Sciences. Use of the HPCAT facility was supported by DOE-BES, DOE-NNSA (CDAC), NSF, DOD-TACOM, and the W. M. Keck Foundation. The University of Alabama authors gratefully acknowledge the support of the NSF MRSEC DMR-0213985.