Journal
PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS
Volume 469, Issue 9-12, Pages 404-412Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.physc.2009.03.033
Keywords
CaFe2As2; Superconductivity; Pressure; Structural phase transition; Magnetic phase transition
Categories
Funding
- Department of Energy, Basic Energy Sciences [DE-AC02-07CH11358]
- National Science Foundation [DMR-0306165, DMR-0805335]
- NSERC
- CIFAR
- Direct For Mathematical & Physical Scien [0805335] Funding Source: National Science Foundation
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At ambient pressure CaFe2As2 has been found to undergo a first order phase transition from a high temperature, tetragonal phase to a low-temperature orthorhombic/antiferromagnetic phase upon cooling through T similar to 170 K. With the application of pressure this phase transition is rapidly suppressed and by similar to 0.35 GPa it is replaced by a first order phase transition to a low-temperature collapsed tetragonal, non-magnetic phase. Further application of pressure leads to an increase of the tetragonal to collapsed tetragonal phase transition temperature, with it crossing room temperature by similar to 1.7 GPa. Given the exceptionally large and anisotropic change in unit cell dimensions associated with the collapsed tetragonal phase, the state of the pressure medium (liquid or solid) at the transition temperature has profound effects on the low-temperature state of the sample. For He-gas cells the pressure is as close to hydrostatic as possible and the transitions are sharp and the sample appears to be single phase at low temperatures. For liquid media cells at temperatures below media freezing, the CaFe2As2 transforms when it is encased by a frozen media and enters into a low-temperature multi-crystallographic-phase state, leading to what appears to be a strain stabilized superconducting state at low temperatures. (C) 2009 Elsevier B.V. All rights reserved.
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