Strong coupling between magnetic and structural order parameters inSrFe2As2

Abstract

X-ray and Neutron diffraction as well as muon spin relaxation and Mössbauer experiments performed on SrFe 2 As 2 polycrystalls confirm a sharp first order transition at T 0 = 205 K corresponding to an orthorhombic phase distortion and to a columnar antiferromagnetic Fe ordering with a propagation vector (1,0,1), and a larger distortion and larger size of the ordered moment than reported for BaFe 2 As 2 . The structural and the magnetic order parameters present an remarkable similarity in their temperature dependence from T 0 down to low temperatures, showing that both phenomena are intimately connected. Accordingly, the size of the ordered Fe moments scale with the lattice distortion when going from SrFe 2 As 2 to BaFe 2 As 2 . Full-potential band structure calculations confirm that the columnar magnetic order and the orthorhombic lattice distortion are intrinsically tied to each other.

Effect of pressure on the magnetostructural transition inSrFe2As2

“…Between 210 K to 205 K, the high-temperature undistorted tetragonal phase disappears abruptly but a small amount of the orthorhombic phase coexists as expected for a first-order phase-transition. Resistivity, ρ(T ), susceptibility, χ(T ), and specific heat, C(T ), measurements show anomalies around 205 K. 18 Our results on poly-and single crystalline SrFe 2 As 2 from high pressure electrical resistivity and X-ray diffraction experiments reveal a suppression of T 0 with increasing pressure and hint to the possible existence of a magnetic instability in the pressure range from 4 to 5 GPa. Resistivity data suggests the emergence of a superconducting phase at p > 2.5 GPa.…”

“…12 In the AFe 2 As 2 compounds, T 0 at ambient pressure corresponds to both the structural transition and to the onset of antiferromagnetic ordering, which are intimately linked together. 7,18 In contrast, it is presently suggested that in the RFeAsO compounds, 4 the antiferromagnetic ordering occurs at approximately 10 − 20 K below the structural ordering. There both transitions are marked by an anomaly in the resistivity.…”

Muon spin rotation study of magnetism and superconductivity in Ba(Fe1−xCox)2Bernhard1, Wang2, Nuccio3 et al. 2012Phys. Rev. B5422871View full textAdd to dashboardCite

“…Its oscillatory signal has a large amplitude and a small relaxation rate similar to that in previous μSR experiments. 22,56,57 The fit shown by the solid line has been obtained with the function…”

Magnetic order in orbital models of the iron pnictides

“…[3][4][5][6] Although this already provides strong motivation to study the magnetism of the pnictides, the unusual magnetic properties are of interest in their own right. 7,8 It is now well established that the undoped cuprates are AFM Mott insulators.…”