Related papers: First Principles Study of CaFe2As2 "Collapse" Unde…
Structural and electronic characterization of (Ca0.67Sr0.33)Fe2As2 has been performed as a func- tion of pressure up to 12 GPa using conventional and designer diamond anvil cells. The compound (Ca0.67Sr0.33)Fe2As2 behaves intermediate…
CaFe$_2$As$_2$ has been synthesized and found to form in the tetragonal, ThCr$_2$Si$_2$ structure with lattice parameters $a = 3.912(68) \AA$ and $c = 11.667(45) \AA$. Upon cooling through 170 K, CaFe$_2$As$_2$ undergoes a first order,…
Low-temperature (22~K) irradiation with 2.5~MeV electrons was used to study the competition between stripe ${\rm C_2}$ and tetragonal ${\rm C_4}$ antiferromagnetic phases which exist in a narrow doping range around $x=$0.25 in hole-doped…
We report high pressure powder synchrotron x-ray diffraction studies on MFe2As2 (M=Ba, Ca) over a range of temperatures and pressures up to about 56 GPa using a membrane diamond anvil cell. A phase transition to a collapsed tetragonal phase…
Using non-resonant Fe K-beta x-ray emission spectroscopy, we reveal that Sr-doping of CaFe2As2 decouples the Fe moment from the volume collapse transition, yielding a collapsed-tetragonal, paramagnetic normal state out of which…
The structural properties of the SrFe2As2 and CaFe2As2 compounds have been extensively analyzed by transmission electron microscopy (TEM) from room temperature down to 20K. The experimental results demonstrate that the SrFe2As2 crystal, in…
We report systematic investigation of high pressure crystal structures and structural phase transition upto 46 GPa in CaFeAsF and 40 GPa in SrFeAsF at 40 K using powder synchrotron x-ray diffraction experiments and Rietveld analysis of the…
Recent high-pressure studies found that superconductivity can be achieved under very low pressure in the parent iron arsenide compound CaFe2As2, although details of the sharpness and temperature of transitions vary between liquid medium and…
We present a systematic pressure study of poly- and single crystalline SrFe2As2 by electrical resistivity and X-ray diffraction measurements. SrFe2As2 exhibits a structural phase transition from a tetragonal to an orthorhombic phase at…
We present an optical spectroscopy study on P-doped CaFe$_2$As$_2$ which experiences a structural phase transition from tetragonal to collapsed tetragonal (cT) phase near 75 K. The measurement reveals a sudden reduction of low frequency…
In a joint experimental and theoretical study, we investigate the isostructural collapse from the ambient pressure tetragonal phase to a collapsed tetragonal phase for non-superconducting metallic SrFe2As2 and SrFe_1.8Ru_0.2As_2. The…
We report on measurements of the magnetic susceptibility and electrical resistance under He-gas pressure on single crystals of Ca(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$. We find that for properly heat-treated crystals with modest…
The density functional non-interacting susceptibility has been analyzed in different phases of CaFe2As2 and compared with similar data for pure d-metals. The conditions for the "no local moment" itinerant state with large frustrations are…
75As-zero-field nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements are performed on CaFe2As2 under pressure. At P = 4.7 and 10.8 kbar, the temperature dependences of nuclear-spin-lattice relaxation rate…
The static and the dynamic spin correlations in the low temperature collapsed tetragonal and the high temperature tetragonal phase in CaFe2As2 have been investigated by 75As nuclear magnetic resonance (NMR) and nuclear quadrupole resonance…
Recently, KFe$_2$As$_2$ was shown to exhibit a structural phase transition from a tetragonal to a collapsed tetragonal phase under applied pressure of about $15~\mathrm{GPa}$. Surprisingly, the collapsed tetragonal phase hosts a…
CaFe2As2 single crystals under uniaxial pressure applied along the c axis exhibit the coexistence of several structural phases at low temperatures. We show that the room-temperature tetragonal phase is stabilized at low temperatures for…
A-122 pnictides (A an alkaline earth element) possess striped antiferromagnetic states of orthorhombic (OR) symmetry and nonmagnetic states of tetragonal (T) symmetry. Based on total energy calculations, we show that the T = 0K…
Temperature dependent measurements of 57Fe Mossbauer spectra on CaFe2As2 single crystals in the tetragonal and collapsed tetragonal phases are reported. Clear features in the temperature dependencies of the isomer shift, relative spectra…
We report $^{75}$As NMR measurements in CaFe$_2$As$_2$, made under applied pressures up to 0.83 GPa produced by a standard clamp pressure cell. Our data reveal phase segregation of paramagnetic (PM) and antiferromagnetic (AFM) phases over a…