Article

# Two-dimensional magnetism in the pnictide superconductor parent material SrFeAsF probed by muon-spin relaxation

Physical review. B, Condensed matter (Impact Factor: 3.66). 11/2008; DOI: 10.1103/PhysRevB.79.060402

Source: arXiv

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**ABSTRACT:**Using first-principles calculation, we study effective electron correlation and spin density fluctuation in iron-based fluorides SrFe1−x Cox AsF (x=0, 0.125). We obtain the observed magnetic moment of Fe atom with a strongly attractive electron correction. Whereas, different from the parent compound, the density of state of superconducting SrFe1−x Cox AsF (x=0.125) near to the Fermi energy is reduced for both signs of effective electron correlation, and suggests strong instability there. In addition, spin density fluctuation resulted from the effective correlation exists in Co-doped compound, may propagate in the form of collective excitation and manifest as spin fluctuation with specific q-vector in momentum space.Journal of Low Temperature Physics 04/2012; 167(1-2). · 1.04 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**In this short review, we attempt to give a comprehensive discussion of studies performed to date by muon-spin spectroscopy (more precisely the relaxation and rotation technique, also know as μSR) on the recently discovered layered iron-based superconductors. On one side, μSR has been used to characterize the magnetic state of different families of layered iron-based systems. Similarly the subtle interplay of the magnetic state and the structural transition present in some families has been investigated. We will also discuss the information provided by this technique on the interaction between the magnetic state and the superconducting phase. Finally the μSR technique has been used to investigate the magnetic penetration depth of the superconducting ground state. The study of its absolute value, temperature and magnetic field dependence provides crucial tests for investigating possible unconventional superconducting states in such systems.Physica C Superconductivity 01/2009; · 1.11 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**The magnetic ordering and crystal structure of iron pnictide SrFeAsF was investigated by using neutron powder-diffraction method. With decreasing temperature, the tetragonal to orthorhombic phase transition is found at 1802 K while the paramagnetic to antiferromagnetic phase-transition set in at 1333 K. The big difference between structural and magnetic phase transitions in SrFeAsF indicates the weak magnetic exchange coupling between Fe layers. Similar to the parent compound of other iron-pnictide system, the striped Fe magnetism is confirmed in antiferromagnetic phase and the Fe moment of 0.586 B aligned along long a axis. Given the fact that long-range antiferromagnetic order can be described by a power law with = 0.12416, SrFeAsF can be treated as a quasi-two-dimensional Ising system. Thermal expansion of orthorhombic phase of SrFeAsF is also investigated. Based on the Grüneisen approximation and Debye approximation for internal energy, the volume of SrFeAsF can be well fitted with Debye temperature of 3475 K. The experimental atomic-displacement parameters for different crystallographic sites in SrFeAsF are analyzed with Debye model. Thermal expansion analysis for SrFeAsF suggested that the expansion of FeAs layers plays an impor-tant role in determining the thermal expansion coefficient.Physical Review B 03/2010; · 3.66 Impact Factor

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