Magnetic neutron diffraction study of Ba(Fe1-xCo x)2As2 critical exponents through the tricritical doping

D. M. Pajerowski, C. R. Rotundu, J. W. Lynn, R. J. Birgeneau

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Abstract

We present temperature dependent magnetic neutron diffraction measurements on Ba(Fe1-xCox)2As2 for x=0.039, 0.022, and 0.021 as-grown single crystals. Our investigations probe the behavior near the magnetic tricritical point in the (x,T) plane, xtr≈0. 022, as well as systematically exploring the character of the magnetic phase transition across a range of doping values. All samples show long-range antiferromagnetic order that may be described near the transition by simple power laws, with β=0.306±0.060 for x=0.039, β=0.208±0. 005 for x=0.022, and β=0.198±0.009 for x=0.021. For the x=0.039 sample, the data are reasonably well described by the order parameter exponent β=0.326 expected for a three-dimensional Ising model while the x=0.022 and x=0.021 samples are near the β=0.25 value for a tricritical system in the mean-field approximation. These results are discussed in the context of existing experimental work and theoretical predictions.

Original languageEnglish
Article number134507
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume87
Issue number13
DOIs
StatePublished - Apr 9 2013
Externally publishedYes

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