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High resolution x-ray scattering studies of structural phase transitions in Cr-doped BaFe2As2

We have performed high resolution x-ray scattering measurements on single crystal samples of Ba(Fe(1-x)Cr(x))2As2 (x = 0 to 0.335). These measurements examine the effect of Cr-doping on the high temperature tetragonal (I4/mmm) to low temperature orthorhombic (Fmmm) structural phase transition of the parent compound BaFe2As2. Increasing Cr concentration is found to suppress the structural transition temperature (Ts), and reduce the magnitude of the orthorhombic strain (delta). The doping dependence of the orthorhombic strain, combined with complementary measurements of the high temperature magnetic susceptibility, suggests the presence of a magnetostructural crossover at x ~ 0.05. In particular, this crossover appears to mark a shift from strong to weak orthorhombicity and from predominantly itinerant to localized magnetic behavior.