Growth, discovery and characterization of single crystalline Pt-Al and Eu-Pt-Al phases*

Recently, a Eu2Pt6Al15 phase synthesized by arc-melting followed by a thermal treatment was reported [1], showing a first order valence transition upon cooling below 50 K. In order to better understand the Pt-Al and Eu-Pt-Al phase space we grew single crystals of Al rich binary and ternary compounds via solution growth [2]. In addition to growing single crystals of PtAl4 [3] we discovered a new polymorph of Eu2Pt6Al15 obtained by high temperature solution growth, built from the same constituent layers as the previously reported one [1], though differently stacked. Despite the similarity between the two Eu2Pt6Al15 phases, the Eu valence and the magnetism have notably different behavior, revealing an interesting sensitivity to the way the layers are stacked. We report on x-ray diffraction, magnetization, resistivity and Mössbauer results to compare all of these phases in their pristine state, as well as their change under different thermal treatments.

[1] Radzieowski, M., et al., J. Am. Chem. Soc. 140, 8950–8957 (2018).

[2] Canfield, P. C. Rep. Prog. Phys. 83 016501 (2020).

[3] Wörle, M., et al., J. Alloys Compd. 455, 130 (2008).