Synthesis, characterization and low temperature studies of iron chalcogenide superconductors

Janaki, J.; Kumary, T. Geetha; Mani, Awadhesh; Kalavathi, S.; Reddy, G. V. R.; Rao, G. Venugopal; Bharathi, A.

doi:10.1016/j.jallcom.2009.07.026

Cited by 40 publications

(40 citation statements)

References 13 publications

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“…Other kind of anomaly commonly observed in the superconducting FeSe samples is a step-like change in the magnetization curve in the ZFC measurement ending around 120 K-130 K [4,7,21], similar to that observed in figure 3 for the commercial sample. Blachowski, et al [20] have reported this kind of anomaly and by means of Mössbauer experiments analysis they adjudicated it to the presence of a hexagonal FeSe phase, specifically to spin rotation transition around 125 K in the hexagonal Fe 7 Se 8 compound.…”

Section: Discussionsupporting

confidence: 79%

Magnetic anomaly in superconducting FeSe

Mendoza

Benítez

Morales

et al. 2010

Solid State Communications

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Synthesis, electrical and magnetic characterization of superconducting FeSe 0.85 compound is reported. An anomaly in the magnetization against temperature around 90K is observed. Magnetic characterization of a commercial compound with nominal FeSe stoichiometry is also presented. The overall magnetic behaviors as well as the magnetic anomaly in both compounds are discussed in terms of magnetic impurities and secondary phases.

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Section: Discussionsupporting

confidence: 79%

Magnetic anomaly in superconducting FeSe

Mendoza

Benítez

Morales

et al. 2010

Solid State Communications

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“…With increasing temperature the peak of SeO 2 disappeared and the main phase became β-FeSe, with a small minority of Ca 4 Fe 9 O 17 . X-ray diffraction indicated that FeSe samples were polycrystalline, similar to the earlier reports [1,12]. The main Ca 4 Fe 9 O 17 peak decreased with increasing temperature, indicating that Ca could enter the Fe sublattice site of FeSe.…”

Section: Methodssupporting

confidence: 87%

Processing and Characterization of Bulk FeSe

Muralidhar¹,

Hanai²,

Furutani³

et al. 2016

JEE

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Abstract:We investigated the effect of processing conditions on the structure and physical properties of the polycrystalline samples of Ca 0.8 Fe 2 Se 2 prepared via solid state reaction. X-ray diffraction showed that the main phase became FeSe when the sintering temperature increased above 350 °C. The temperature dependence of magnetization (M-T curves) recorded in zero-field-cooled mode by SQUID magnetometer showed some bumps at around 120 K to 140 K. These bumps moved to lower temperatures when the processing temperature increased above 550 °C. On the other hand, pure FeSe materials produced at 900 °C for 24 h showed a sharp superconducting transition T c,onset = 8.16 K and the critical current density of 6,252 A/cm 2 at 5 K, self-field. SEM results indicated an enhanced grain connectivity.

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“…Further, in the normal state, sample S2 displays a metallic behavior ͑d / dT Ͼ 0͒ whereas a ϰ log 1 / T divergence was observed for S1 below a temperature T a ϳ 130 K. A similar divergence is also reported by Liu et al for Fe 1.11 Te 0.64 Se 0.36 below 50 K. 25 They also found a kink in resistivity at 120 K. The authors associated this kink with the magnetic anomaly observed earlier in polycrystalline samples. 10 On the other hand, Janaki et al 27 attributed a similar anomaly observed around 125 K in the magnetization measurement of their polycrystalline samples to the Verwey transition of a Fe 3 O 4 spurious phase within the grain boundaries. In the present case, however, a −log T divergence in ͑T͒ appears below T a , where an anomaly in the magnetization is observed ͑see Fig.…”

Section: Resultsmentioning

confidence: 81%

Disorder-driven electronic localization and phase separation in superconductingFe1+yTe0.5Se0.5<

et al. 2010

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We have investigated the influence of Fe excess on the electrical transport and magnetism of Fe 1+y Te 0.5 Se 0.5 ͑y = 0.04 and 0.09͒ single crystals. Both compositions exhibit resistively determined superconducting transitions ͑T c ͒ with an onset temperature of about 15 K. From the width of the superconducting transition and the magnitude of the lower critical field H c1 , it is inferred that excess of Fe suppresses superconductivity. The linear and nonlinear responses of the ac susceptibility show that the superconducting state for these compositions is inhomogeneous. A possible origin of this phase separation is a magnetic coupling between Fe excess occupying interstitial sites in the chalcogen planes and those in the Fe-square lattice. The temperature derivative of the resistivity d / dT in the temperature range T c Ͻ T Ͻ T a with T a being the temperature of a magnetic anomaly, changes from positive to negative with increasing Fe. A log 1 / T divergence of the resistivity above T c in the sample with higher amount of Fe suggests a disorder-driven electronic localization.

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Synthesis, characterization and low temperature studies of iron chalcogenide superconductors

Cited by 40 publications

References 13 publications

Magnetic anomaly in superconducting FeSe

Magnetic anomaly in superconducting FeSe

Processing and Characterization of Bulk FeSe

Disorder-driven electronic localization and phase separation in superconductingFe1+yTe0.5Se0.5<

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