Heat capacity study of BaFe${}_2$As${}_2$: effects of annealing

Abstract

Heat-capacity, X-ray diffraction, and resistivity measurements on a high-quality BaFe${}_2$As${}_2$ sample show an evolution of the magneto-structural transition with successive annealing periods. After a 30-day anneal the resistivity in the (ab) plane decreases by more than an order of magnitude, to 12 $\mu \Omega$cm, with a residual resistance ratio $\sim$36; the heat-capacity anomaly at the transition sharpens, to an overall width of less than K, and shifts from 135.4 to 140.2 K. The heat-capacity anomaly in both the as-grown sample and after the 30-day anneal shows a hysteresis of $\sim$0.15 K, and is unchanged in a magnetic field ${\mu }_0$H = 14 T. The X-ray and heat-capacity data combined suggest that there is a first order jump in the structural order parameter. The entropy of the transition is reported.

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• Continuous magnetic and structural phase transitions in Fe1+yTe
• Effect of annealing on the specific heat of Ba(Fe1-xCox)2As2
• First and second order magnetic and structural transitions in BaFe${}_{2(1-x)}$Co${}_{2x}$As${}_2$
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• Specific heat of Ba${}_{0.59}$K${}_{0.41}$Fe${}_2$As${}_2$, and a new method for identifying the electron contribution: two electron bands with different energy gaps in the superconducting state
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• Phase transition in CaFeAsH: bridging 1111 and 122 iron-based superconductors
• Strain-activated structural anisotropy in BaFe2As2
• Lattice Disorder Effect on Magnetic Ordering of Iron Arsenides
• Multiple magnetic orders discovered in the superconducting state of EuFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$