First-order phase transitions in the ThCr2Si2-type phosphides ARh2P2 (A = Sr, Eu)

Huhnt, C.; Michels, G.; Roepke, M. H.; Schlabitz, W.; Wurth, A.; Johrendt, Dirk; Mewis, A.

doi:10.1016/s0921-4526(97)00431-6

Cited by 42 publications

(30 citation statements)

References 14 publications

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“…We also note that pressure-induced superconductivity in CaFe 2 As 2 has been observed close to the OcT transition, and within the hysteretic region associated with that transition and, therefore, should be studied carefully under hydrostatic conditions. The loss of magnetism in the cT phase is largely due to changes in the band structure that depletes Fe 3d DOS at E F , a behavior that is analogous to other 122 type compounds 19,20,21,23 and qualitatively consistent with previous theoretical calculations. 15,24,26 …”

Section: Discussionsupporting

confidence: 87%

Lattice collapse and quenching of magnetism inCaFe2As2under pressure: A single-crystal neutron and x-ray diffraction investigation

et al. 2009

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Single crystal neutron and high-energy x-ray diffraction have identified the phase lines corresponding to transitions between the ambient-pressure tetragonal (T), the antiferromagnetic orthorhombic (O) and the nonmagnetic collapsed tetragonal (cT) phases of CaFe2As2. We find no evidence of additional structures for pressures up to 2.5 GPa (at 300 K). Both the T-cT and O-cT transitions exhibit significant hysteresis effects and we demonstrate that coexistence of the O and cT phases can occur if a non-hydrostatic component of pressure is present. Measurements of the magnetic diffraction peaks show no change in the magnetic structure or ordered moment as a function of pressure in the O phase and we find no evidence of magnetic ordering in the cT phase. Band structure calculations show that the transition results in a strong decrease of the iron 3d density of states at the Fermi energy, consistent with a loss of the magnetic moment.PACS numbers: 61.50. Ks, 61.05.fm, 74.70.Dd The discovery 1,2 of pressure-induced superconductivity in CaFe 2 As 2 has opened an exciting new avenue for investigations of the relationship between magnetism, superconductivity, and lattice instabilities in the iron arsenide family of superconductors. Features found in the compositional phase diagrams of the iron arsenides, 3 such as a superconducting region at low temperature and finite doping concentrations, are mirrored in the pressure-temperature phase diagrams. Superconductivity appears at either a critical doping, or above some critical pressure in the AFe 2 As 2 (A=Ba, Sr, Ca) or '122' family of compounds, raising questions regarding the role of both electronic doping and pressure, especially in light of the recent observation of pressure induced superconductivity in the related compound, LaFeAsO.4 Does doping simply add charge carriers, or are changes in the chemical pressure, upon doping, important as well? What subtle, or striking, modifications in structure or magnetism occur with doping or pressure, and how are they related to superconductivity? Similar to other members of the AFe 2 As 2 (A=Ba, Sr) family, 5,6,7,8 at ambient pressure CaFe 2 As 2 undergoes a transition from a non-magnetically ordered tetragonal (T) phase (a = 3.879(3)Å, c = 11.740(3)Å) to an antiferromagnetic (AF) orthorhombic (O) phase (a = 5.5312(2)Å, b = 5.4576(2)Å, c = 11.683(1)Å) below approximately 170 K.9,10 In the O phase, Fe moments order in the so called AF2 structure 11 with moments directed along the aaxis of the orthorhombic structure.10 Neutron powder diffraction measurements 12 of CaFe 2 As 2 under hydrostatic pressure found that for p>0.35 GPa (at T=50 K), the antiferromagnetic O phase transforms to a new, non-magnetically ordered, collapsed tetragonal (cT) structure (a = 3.9792(1)Å, c = 10.6379(6)Å) with a dramatic decrease in both the unit cell volume (5%) and the c/a ratio (11%). The transition to the cT phase occurs in close proximity to the pressure at which superconductivity is first observed. 1 Total energy calculations based on this cT s...

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Section: Discussionsupporting

confidence: 87%

Lattice collapse and quenching of magnetism inCaFe2As2under pressure: A single-crystal neutron and x-ray diffraction investigation

et al. 2009

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“…16 Previous investigations in BaRh 2 P 2 did not show any structural transition up to 11 GPa and down to low temperatures 18 ͑no reports for BaIr 2 P 2 ͒. In the phoshpides, unlike the arsenides, proximity to a structural transition is not a prerequisite for SC.…”

Section: H C2mentioning

confidence: 85%

“…17 Isostructural transitions ͑tetragonal to collapsed tetragonal͒ have also been reported in the ternary phosphides under pressure. 18,19 Unlike their As counterparts, these compounds do not show a concomitant magnetic transition, 16 except EuCo 2 P 2 with its Eu moment ordering. 20 This Rapid Communication reports on single-crystal SC in the Co column for the 122 phosphides, namely, in BaIr 2 P 2 and BaRh 2 P 2 .…”

mentioning

confidence: 91%

Superconductivity without Fe or Ni in the phosphidesBaIr2P2andBaRh2P
Berry
¹
,
Capan
²
,
Seyfarth
³

et al. 2009
Phys. Rev. B
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“…23 The fact that 3Å is the average value between covalent and Van der Waals radii of both elemental As and P (Ref. 21) suggests that this striking universal behavior can be observed in any system with similar p-orbital overlap approaching this critical value.…”

mentioning

confidence: 99%

Structural collapse and superconductivity in rare-earth-doped CaFe2As2

et al. 2012

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Aliovalent rare earth substitution into the alkaline earth site of CaFe2As2 single-crystals is used to fine-tune structural, magnetic and electronic properties of this iron-based superconducting system. Neutron and single crystal x-ray scattering experiments indicate that an isostructural collapse of the tetragonal unit cell can be controllably induced at ambient pressures by choice of substituent ion size. This instability is driven by the interlayer As-As anion separation, resulting in an unprecedented thermal expansion coefficient of 180 × 10 −6 K −1 . Electrical transport and magnetic susceptibility measurements reveal abrupt changes in the physical properties through the collapse as a function of temperature, including a reconstruction of the electronic structure. Superconductivity with onset transition temperatures as high as 47 K is stabilized by the suppression of antiferromagnetic order via chemical pressure, electron doping or a combination of both. Extensive investigations are performed to understand the observations of partial volume-fraction diamagnetic screening, ruling out extrinsic sources such as strain mechanisms, surface states or foreign phases as the cause of this superconducting phase that appears to be stable in both collapsed and uncollapsed structures.

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First-order phase transitions in the ThCr2Si2-type phosphides ARh2P2 (A = Sr, Eu)

Cited by 42 publications

References 14 publications

Lattice collapse and quenching of magnetism inCaFe2As2under pressure: A single-crystal neutron and x-ray diffraction investigation

Lattice collapse and quenching of magnetism inCaFe2As2under pressure: A single-crystal neutron and x-ray diffraction investigation

Superconductivity without Fe or Ni in the phosphidesBaIr2P2andBaRh2P
Berry
¹
,
Capan
²
,
Seyfarth
³

et al. 2009
Phys. Rev. B
42
10
45
0
View full text Add to dashboard Cite

Structural collapse and superconductivity in rare-earth-doped CaFe2As2

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First-order phase transitions in the ThCr2Si2-type phosphides ARh2P2 (A = Sr, Eu)

Cited by 42 publications

References 14 publications

Lattice collapse and quenching of magnetism inCaFe2As2under pressure: A single-crystal neutron and x-ray diffraction investigation

Lattice collapse and quenching of magnetism inCaFe2As2under pressure: A single-crystal neutron and x-ray diffraction investigation

Superconductivity without Fe or Ni in the phosphidesBaIr2P2andBaRh2PBerry1, Capan2, Seyfarth3 et al. 2009Phys. Rev. B4210450View full textAdd to dashboardCite

Structural collapse and superconductivity in rare-earth-doped CaFe2As2

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Product

Resources

About

Superconductivity without Fe or Ni in the phosphidesBaIr2P2andBaRh2P
Berry
¹
,
Capan
²
,
Seyfarth
³

et al. 2009
Phys. Rev. B
42
10
45
0
View full text Add to dashboard Cite