Recoilless fraction studies of iron near the Curie temperature

Kolk, Berend van der; Bleloch, Andrew; Hall, David B.

doi:10.1007/bf02399490

Cited by 14 publications

(4 citation statements)

References 7 publications

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“…With decreasing temperature, the center of H low moves slightly to the higher field side, while the center of H high is almost invariable. At 30 K, profiles of the P(H) retain bimodal for both compounds and the little bump around 1.2 T in the P(H) of x = 0.016 is ascribed to the saturation effect [21]. The center position of H low is 3.2(1) T at a doping level of x = 0.016, slightly smaller than that of x = 0.064 [3.7(3) T], while the center positions of H high are about 5.4 T for both samples, as shown in figure 3, a value which is close to the reported hyperfine field of BaFe 2 As 2 at 4.2 K [12].…”

Section: Mössbauer Resultsmentioning

confidence: 92%

Magnetic properties and spin dynamics in Ba(Fe_1−xMn_x)₂As₂compounds studied by⁵⁷Fe Mössbauer spectroscopy

Ma¹,

Bai²,

Li³

et al. 2013

J. Phys.: Condens. Matter

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Ba(Fe(1-x)Mn(x))2As2 compounds with x = 0.016 and 0.064 have been studied by (57)Fe Mössbauer spectroscopy in the temperature range from 30 to 300 K. The unusual magnetic splitting spectra at lower temperatures have been analyzed using the distribution of hyperfine field. It is found that the influence of Mn dopant spreads beyond the nearest Fe magnetic moments, and the Fe 3d electrons behave more localized compared with those in the electron-doped compounds. This reduces the hyperfine interactions between iron nucleus and the sounding electrons. The shape of the spin density wave is near-rectangular at 6.4%-Mn doping, indicating quite different interband interactions compared with electron-doped compounds. A distinct broadening of the spectral linewidth around the spin density wave transition temperature has been observed and the spin correlation time is deduced according to the linewidth. The correlation time is further related to the spin-lattice relaxation rate by a simple model and the magnetic fluctuations can be explored effectively. It is found that the magnetic fluctuations of iron spins in Mn-doped compounds can be described well using a phenomenological two-component model and the resulting Curie-Weiss temperature is far from the quantum critical point at the present doping levels.

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Section: Mössbauer Resultsmentioning

confidence: 92%

Magnetic properties and spin dynamics in Ba(Fe_1−xMn_x)₂As₂compounds studied by⁵⁷Fe Mössbauer spectroscopy

Ma¹,

Bai²,

Li³

et al. 2013

J. Phys.: Condens. Matter

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“…Usually the sudden increase in the spectra area is an indicator of the appearance of magnetism due to saturation effect, i.e. the magnetic splitting of the energy levels of a 57 Fe nucleus always accompanies an abrupt expansion of the spectral area [36]. However, magnetically splitting is not observable till the limit temperature of the present measurements.…”

Section: Resultsmentioning

confidence: 62%

Phase separation in Ca_1−xLa_xFe₂As₂superconductors: a⁵⁷Fe Mössbauer study

Liu¹,

Li²,

Wan³

et al. 2016

J. Phys.: Condens. Matter

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We report a detailed 57Fe Mössbauer study of lanthanum doped CaFe2As2 superconductors. The quadrupole splitting distribution (QSD) method was adopted to analyze the Mössbauer spectra of Ca(1-x) La(x)Fe2As2 (x = 0.2, 0.3) single crystals. For both compounds we observed two QSD contributions centered at 0.31 mm s(-1) and -0.32 mm s(-1) at room temperature. The first principles calculations of the electronic structures and the electric field gradient (EFG) of Ca(1-y)La(y)Fe2As2 model systems reveal that the EFG changes from positive to negative with increasing dopant concentration, indicating that the La atoms distribute heterogeneously in the compounds. The two QSD components behave differently with decreasing temperature. The minority La-rich phase undergoes superconducting transition, while short range spin fluctuations and/or spin-phonon coupling appear in the majority La-poor phase. Our experiments provide new evidence of the phase separation picture at low temperatures in Ca(1-x)La(x)Fe2As2 superconductors.

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“…The broadening of the spectral width usually represents fluctuation of the surrounding electromagnetic environments experienced by the 57 Fe nucleus, where a magnetic fluctuation is one of the possibilities. In Mössbauer measurements, the appearance of magnetism always associates with the saturation effect [10], which will be firstly characterized by the increase of the spectral area, i.e., the magnetic splitting of the energy levels of a 57 Fe nucleus always accompanies an abrupt expansion of the spectral area. It is found that a sharp increase of Γ starts from around 50 K. Though the increase in area is not so distinct then, it is reasonable to deduce that short-range magnetic fluctuations in the FeAs layer occur above T onset .…”

Section: Results and Analysis -mentioning

confidence: 99%

Mössbauer study of magnetic fluctuation in the iron-arsenic layer of Sr ₂ VO ₃ FeAs

Wan

Liu

et al. 2014

EPL

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Mössbauer spectra of the freshly prepared Sr2VO3FeAs compound have been measured under different temperatures. We observed a variation of the spectral shape with decreasing temperature. The obvious diminution of quadrupole splitting occurred at about 63 K is ascribed to the weak influence of the ferromagnetic transition of the V-O layer to the spatial distribution of Fe-3d electrons, whereas the influence of the antiferromagnetic transition in the V-O layer is negligible. Below the superconducting transition temperature the distinct enhancement of the spectral area and the simultaneous increase of the line width suggest the emergence of magnetic fluctuations in the FeAs layer. Our experimental results strongly indicate the coexistence of magnetism and superconductivity in the freshly prepared Sr2VO3FeAs compound.

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Recoilless fraction studies of iron near the Curie temperature

Cited by 14 publications

References 7 publications

Magnetic properties and spin dynamics in Ba(Fe_1−xMn_x)₂As₂compounds studied by⁵⁷Fe Mössbauer spectroscopy

Magnetic properties and spin dynamics in Ba(Fe_1−xMn_x)₂As₂compounds studied by⁵⁷Fe Mössbauer spectroscopy

Phase separation in Ca_1−xLa_xFe₂As₂superconductors: a⁵⁷Fe Mössbauer study

Mössbauer study of magnetic fluctuation in the iron-arsenic layer of Sr ₂ VO ₃ FeAs

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Recoilless fraction studies of iron near the Curie temperature

Cited by 14 publications

References 7 publications

Magnetic properties and spin dynamics in Ba(Fe1−xMnx)2As2compounds studied by57Fe Mössbauer spectroscopy

Magnetic properties and spin dynamics in Ba(Fe1−xMnx)2As2compounds studied by57Fe Mössbauer spectroscopy

Phase separation in Ca1−xLaxFe2As2superconductors: a57Fe Mössbauer study

Mössbauer study of magnetic fluctuation in the iron-arsenic layer of Sr 2 VO 3 FeAs

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Magnetic properties and spin dynamics in Ba(Fe_1−xMn_x)₂As₂compounds studied by⁵⁷Fe Mössbauer spectroscopy

Magnetic properties and spin dynamics in Ba(Fe_1−xMn_x)₂As₂compounds studied by⁵⁷Fe Mössbauer spectroscopy

Phase separation in Ca_1−xLa_xFe₂As₂superconductors: a⁵⁷Fe Mössbauer study

Mössbauer study of magnetic fluctuation in the iron-arsenic layer of Sr ₂ VO ₃ FeAs