First order structural phase transition in CaFe$_2$As$_2$

N. Ni; S. Nandi; A. Kreyssig; A. I. Goldman; E. D. Mun; S. L. Bud'ko,; P. C. Canfield

arXiv:0806.4328·cond-mat.str-el·November 13, 2009

First order structural phase transition in CaFe$_2$As$_2$

N. Ni, S. Nandi, A. Kreyssig, A. I. Goldman, E. D. Mun, S. L. Bud'ko,, P. C. Canfield

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TL;DR

CaFe$_2$As$_2$ undergoes a first-order structural phase transition from tetragonal to orthorhombic at 170 K, with clear evidence from multiple measurements, making it a key material for studying doping-induced superconductivity.

Contribution

This paper reports the synthesis and characterization of CaFe$_2$As$_2$, revealing its first-order phase transition and positioning it as a promising candidate for superconductivity research.

Findings

01

First-order structural phase transition at 170 K

02

Transition involves tetragonal to orthorhombic change

03

Coexistence and hysteresis observed during transition

Abstract

CaFe $_{2}$ As $_{2}$ has been synthesized and found to form in the tetragonal, ThCr $_{2}$ Si $_{2}$ structure with lattice parameters $a = 3.912 (68) \overset{˚}{A}$ and $c = 11.667 (45) \overset{˚}{A}$ . Upon cooling through 170 K, CaFe $_{2}$ As $_{2}$ undergoes a first order, structural phase transition to a low temperature, orthorhombic phase with a $2 - 3$ K range of hysteresis and coexistence. This transition is clearly evident in microscopic, thermodynamic and transport measurements. CaFe $_{2}$ As $_{2}$ is the third member of the AFe $_{2}$ As $_{2}$ (A = Ba, Sr, Ca) family to exhibit such a dramatic phase transition and is a promising candidate for studies of doping induced superconductivity.

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