Domain structure effect on the superconductivity of BaFePtAs2

Abstract

We report the magnetic properties of BaFePtAs2 compound in a wide temperature range of 5-300 K in the field up to 9 Tesla. The first syntheses of this compound were obtained by conventional solid state reaction technique. The compound crystallizes in the ThCr2Si2-type structure with the space group of I4/mmm. This compound exhibits a superconducting phase transition at around 20 K in low field magnetization data. We do not observe zero resistance at this temperature, presumably due to some impurities scattering mechanisms. But, the sample has tendency to gradually lose resistance with decreasing temperature starting at around 7 K. Some significant features were observed in the low field magnetization data. The most striking one is the observed giant diamagnetic contribution to the magnetization below 100 K. Magnetic susceptibility measurements reveal that diamagnetism in the sample is closely correlated with the magnetic structure in the demagnetized state. We observe that diamagnetism is significantly enhanced by thermal treatments. The relationship between the magnetic structure and diamagnetism is discussed by considering the existing theories.High-field magnetization studies offer a typical magnetic behavior of weak ferromagnets in overall temperature range. On other hand, we clearly observe superconducting M versus H loop at T=5 K. All these results point to a typical of the superconducting weak ferromagnet. As a result, we have examined here a possibility of the coexistence of ferromagnetism and superconductivity in this compound considering the other well-known superconducting ferromagnets in the literature.