title: Anomalous magneto-elastic and charge doping effects in thallium-doped BaFe2As2.
abstract: Within the BaFe2As2 crystal lattice, we partially substitute thallium for barium and report the effects of interlayer coupling in Ba(1-x)Tl(x)Fe2As2 crystals. We demonstrate the unusual effects of magneto-elastic coupling and charge doping in this iron-arsenide material, whereby Néel temperature rises with small x, and then falls with additional x. Specifically, we find that Néel and structural transitions in BaFe2As2 (T(N) = T(s) = 133 K) increase for x = 0.05 (T(N) = 138 K, T(s) = 140 K) from magnetization, heat capacity, resistivity, and neutron diffraction measurements. Evidence from single crystal X-ray diffraction and first principles calculations attributes the stronger magnetism in x = 0.05 to magneto-elastic coupling related to the shorter intraplanar Fe-Fe bond distance. With further thallium substitution, the transition temperatures decrease for x = 0.09 (T(N) = T(s) = 131 K), and this is due to charge doping. We illustrate that small changes related to 3d transition-metal state can have profound effects on magnetism.
authors: Materials Science &Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, US.
authors: Athena S
authors: AS
authors: Sefat
authors: Materials Science &Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, US.
authors: Li
authors: L
authors: Li
authors: Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, US.
authors: Huibo B
authors: HB
authors: Cao
authors: Materials Science &Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, US.
authors: Michael A
authors: MA
authors: McGuire
authors: Materials Science &Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, US.
authors: Brian
authors: B
authors: Sales
authors: Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, US.
authors: Radu
authors: R
authors: Custelcean
authors: Materials Science &Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, US.
authors: David S
authors: DS
authors: Parker