(A=Rb, Cs) via synchrotron Mössbauer spectroscopy*

EuAFe₄As₄(A=Rb, Cs) is a recent addition to the iron-based superconductors. EuAFe₄As₄exhibits peculiar properties with coexistence of superconductivity (T_C ~ 35 K) and ferromagnetism from local moment in divalent Eu (T_m~15 K) [1–4]. The application of pressure suppresses superconductivity and enhance magnetic ordering temperature [5,6] with a crossover of T_C and T_m around 7 GPa [5]. We have investigated the magnetic and valence state in Eu ions via synchrotron Mössbauer spectroscopy in ¹⁵¹Eu in diamond anvil cell. The detailed changes of Eu’s magnetism and local magnetic phase diagram will be discussed.

[1] Y. Liu et al., Phys. Rev. B 93, 214503 (2016).
[2] Y. Liu et al., Sci. Bull. 61, 1213 (2016).
[3] K. Iida et al., Phys. Rev. B 100, 1 (2019).
[4] J.-K. Bao et al., Cryst. Growth Des. (2018).
[5] D. E. Jackson et al., Phys. Rev. B 98, 014518 (2018).
[6] L. Xiang et al., Phys. Rev. B 99, 1 (2019).