Mossbauer studies of helimagnetic FeAs

Kulshreshtha, S. K.; Raj, P.

doi:10.1088/0305-4608/9/11/015

Cited by 25 publications

(27 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…285 K Mössbauer temperature obtained from the second-order Doppler shift in FeAs, Ref. 38 and the line in the lower inset of Fig. 10, is very close to 294 K observed herein for LaFeAsO.…”

Section: F Magnetic Propertiessupporting

confidence: 86%

Phase transitions in LaFeAsO: Structural, magnetic, elastic, and transport properties, heat capacity and Mössbauer spectra

et al. 2008

View full text Add to dashboard Cite

We present results from a detailed experimental investigation of LaFeAsO, the parent material in the series of "FeAs" based oxypnictide superconductors. Upon cooling, this material undergoes a tetragonalorthorhombic crystallographic phase transition at ϳ160 K followed closely by an antiferromagnetic ordering near 145 K. Analysis of these phase transitions using temperature dependent powder x-ray and neutrondiffraction measurements is presented. A magnetic moment of ϳ0.35 B per iron is derived from Mössbauer spectra in the low-temperature phase. Evidence of the structural transition is observed at temperatures well above the transition temperature ͑up to near 200 K͒ in the diffraction data as well as the polycrystalline elastic moduli probed by resonant ultrasound spectroscopy measurements. The effects of the two phase transitions on the transport properties ͑resistivity, thermal conductivity, Seebeck coefficient, and Hall coefficient͒, heat capacity, and magnetization of LaFeAsO are also reported, including a dramatic increase in the magnitude of the Hall coefficient below 160 K. The results suggest that the structural distortion leads to a localization of carriers on Fe, producing small local magnetic moments which subsequently order antiferromagnetically upon further cooling. Evidence of strong electron-phonon interactions in the high-temperature tetragonal phase is also observed.

show abstract

“…285 K Mössbauer temperature obtained from the second-order Doppler shift in FeAs, Ref. 38 and the line in the lower inset of Fig. 10, is very close to 294 K observed herein for LaFeAsO.…”

Section: F Magnetic Propertiessupporting

confidence: 86%

Phase transitions in LaFeAsO: Structural, magnetic, elastic, and transport properties, heat capacity and Mössbauer spectra

et al. 2008

View full text Add to dashboard Cite

show abstract

“…Thus, it is considered that the iron has the features of covalent bonding and itinerant d-electrons to some extent. The suggestion is further supported by the fact that similar values for the isomer shifts have been reported in covalent Fe compounds such as FeAs, which has an isomer shift of 0.47 mm/s at 295 K. [18][19][20] …”

Section: Resultssupporting

confidence: 69%

Spin Ordering in LaFeAsO and Its Suppression in F-Doped Superconductors LaFeAsO_1-xF_xProbed by Mössbauer Spectroscopy

et al. 2008

View full text Add to dashboard Cite

“…The isomer shifts of both the F-doped superconductor and the parent LaFeAsO increase with decreasing temperature as tabulated in Table I. They exhibit similar It has a helimagnetic spin structure with rotated magnetic moments of internal magnetic fields between 4.8 and 1.6 T below the Néel temperature of 77 K and a quadrupole splitting of 0.55 mm/s at 295 K. 13,14) Fe 2 As is another iron-arsenic covalent compound and has a Néel temperature of 353 K. The iron in Fe 2 As, which contains two sites with internal magnetic fields of $13 and 16 T, has isomer shifts of $0:5 and 0.7 mm/s with quadrupole splittings of $À0:1 and À0:5 mm/s, respectively, at 5 K. 15,16) In comparison with the internal magnetic field, the magnetic moments observed in LaFeAsO are roughly similar to those in FeAs, but smaller than those in Fe 2 As. On the other hand, the observed quadrupole splittings are small or almost zero in both the F-doped and parent LaFeAsO.…”

mentioning

confidence: 87%

Spin Ordering in LaFeAsO and Its Suppression in Superconductor LaFeAsO_0.89F_0.11 Probed by Mössbauer Spectroscopy

et al. 2008

View full text Add to dashboard Cite

57 Fe Mössbauer spectroscopy was applied to an iron-based layered superconductor LaFeAsO 0:89 F 0:11 with a transition temperature of 26 K and to its parent material LaFeAsO. Throughout the temperature range from 4.2 to 298 K, a singlet pattern with no magnetic splitting was observed in the Mössbauer spectrum of the F-doped superconductor. Furthermore, no additional internal magnetic field was observed for the spectrum measured at 4.2 K under a magnetic field of 7 T. On the other hand, magnetically split spectra were observed in the parent LaFeAsO below 140 K, and this temperature is slightly lower than that of a structural phase transition from tetragonal to orthorhombic phase, which accompanies the electrical resistivity anomaly at around 150 K. The magnetic moment is estimated to be $0:35 B /Fe from the internal magnetic field of 5.3 T at 4.2 K in the orthorhombic phase, and the spin disorder appears to remain in the magnetically ordered state even at 4.2 K. The lack of a magnetic transition in LaFeAsO 0:89 F 0:11 down to 4.2 K suggests that this system exhibits a paramagnetic state or that the magnetic moment is small. The present results show that F doping effectively suppresses the magnetic and structural transitions in the parent material, leading to the emergence of superconductivity in the F-doped system.

show abstract

Mossbauer studies of helimagnetic FeAs

Cited by 25 publications

References 19 publications

Phase transitions in LaFeAsO: Structural, magnetic, elastic, and transport properties, heat capacity and Mössbauer spectra

Phase transitions in LaFeAsO: Structural, magnetic, elastic, and transport properties, heat capacity and Mössbauer spectra

Spin Ordering in LaFeAsO and Its Suppression in F-Doped Superconductors LaFeAsO_1-xF_xProbed by Mössbauer Spectroscopy

Spin Ordering in LaFeAsO and Its Suppression in Superconductor LaFeAsO_0.89F_0.11 Probed by Mössbauer Spectroscopy

Contact Info

Product

Resources

About

Mossbauer studies of helimagnetic FeAs

Cited by 25 publications

References 19 publications

Phase transitions in LaFeAsO: Structural, magnetic, elastic, and transport properties, heat capacity and Mössbauer spectra

Phase transitions in LaFeAsO: Structural, magnetic, elastic, and transport properties, heat capacity and Mössbauer spectra

Spin Ordering in LaFeAsO and Its Suppression in F-Doped Superconductors LaFeAsO1-xFxProbed by Mössbauer Spectroscopy

Spin Ordering in LaFeAsO and Its Suppression in Superconductor LaFeAsO0.89F0.11 Probed by Mössbauer Spectroscopy

Contact Info

Product

Resources

About

Spin Ordering in LaFeAsO and Its Suppression in F-Doped Superconductors LaFeAsO_1-xF_xProbed by Mössbauer Spectroscopy

Spin Ordering in LaFeAsO and Its Suppression in Superconductor LaFeAsO_0.89F_0.11 Probed by Mössbauer Spectroscopy