Synthesis and Properties of CaFe$_2$As$_2$ Single Crystals

TL;DR

This paper reports the synthesis and characterization of CaFe2As2 single crystals, revealing a first-order phase transition at 171 K and detailed electronic and magnetic properties relevant to iron-based superconductors.

Contribution

The study provides the first detailed synthesis and physical property measurements of CaFe2As2 single crystals, expanding understanding of iron arsenide compounds related to superconductivity.

Findings

First-order phase transition at 171 K observed in susceptibility, resistivity, and heat capacity.

Nearly isotropic magnetic susceptibility from 2 K to 350 K.

Negative Hall coefficient indicating dominant n-type carriers.

Abstract

We report the synthesis and basic physical properties of single crystals of CaFe2As2, an isostructural compound to BaFe2As2 which has been recently doped to produce superconductivity. CaFe2As2 crystalizes in the ThCr2Si2 structure with lattice parameters a = 3.907(4) A and c = 11.69(2) A. Magnetic susceptibility, resistivity, and heat capacity all show a first order phase transition at T_0 171 K. The magnetic susceptibility is nearly isotropic from 2 K to 350 K. The heat capacity data gives a Sommerfeld coefficient of 8.2 +- 0.3 mJ/molK2, and does not reveal any evidence for the presence of high frequency (> 300 K) optical phonon modes. The Hall coefficient is negative below the transition indicating dominant n-type carriers.