Paramagnetic Spin Correlations in CaFe2As2 Single Crystals

Journal Article · Fri Jan 01 00:00:00 EST 2010 · Physical Review B

DOI:https://doi.org/10.1103/PhysRevB.81.214407· OSTI ID:982410

Omar Diallo, Souleymane ^[1]; Pratt, Daniel ^[2]; Fernandes, Rafael ^[2]; Tian, Wei ^[2]; Zarestky, J. L. ^[2]; Lumsden, Mark D ^[1]; Perring, T. G. ^[3]; Broholm, C. ^[4]; Ni, Ni ^[2]; Budko, S L ^[2]; Canfield, Paul ^[2]; Li, Haifeng ^[2]; Vaknin, D ^[2]; Kreyssig, A. ^[2]; Goldman, A. I. ^[2]; Mcqueeney, R J ^[2]

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1. ORNL
2. Ames Laboratory and Iowa State University
3. ISIS Facility, Rutherford Appleton Laboratory
4. Johns Hopkins University

Magnetic correlations in the paramagnetic phase of CaFe2As2(TN=172 K) have been examined by means of inelastic neutron scattering from 180 K ( 1.05TN) up to 300 K (1.8TN). Despite the first-order nature of the magnetic ordering, strong but short-ranged antiferromagnetic (AFM) correlations are clearly observed. These correlations, which consist of quasielastic scattering centered at the wave vector QAFM of the low-temperature AFM structure, are observed up to the highest measured temperature of 300 K and at high energy transfer ( >60 meV). The L dependence of the scattering implies rather weak interlayer coupling in the tetragonal c direction corresponding to nearly two-dimensional fluctuations in the (ab) plane. The spin correlation lengths within the Fe layer are found to be anisotropic, consistent with underlying fluctuations of the AFM stripe structure. Similar to the cobalt-doped superconducting BaFe2As2 compounds, these experimental features can be adequately reproduced by a scattering model that describes short-ranged and anisotropic spin correlations with overdamped dynamics.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). High Flux Isotope Reactor (HFIR)
• Sponsoring Organization: USDOE
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 982410
• Journal Information: Physical Review B, Vol. 81, Issue 21; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ENERGY TRANSFER
FLUCTUATIONS
MONOCRYSTALS
NEUTRONS
SCATTERING
SPIN
VECTORS
Neutron Scattering
Iron Arsenides
Superconductors