The study of Eu intermetallic compounds has allowed the exploration of valence fluctuations and transitions in $4f$ electron systems. Recently, a ${\mathrm{Eu}}_2{\mathrm{Pt}}_6{\mathrm{Al}}_{15}$ phase synthesized by arc-melting followed by a thermal treatment was reported M. Radzieowski et al. [J. Am. Chem. Soc. 140, 8950 (2018)], which undergoes a transition upon cooling below 45 K that was interpreted as a valence transition from ${\mathrm{Eu}}^{2+}$ to ${\mathrm{Eu}}^{3+}$. In this paper, we present the discovery of another polymorph of ${\mathrm{Eu}}_2{\mathrm{Pt}}_6{\mathrm{Al}}_{15}$ obtained by high temperature solution growth, which presents different physical properties than the arc-melted polycrystalline sample. Despite the similarities in crystal structure and chemical composition, the Eu valence transition is almost fully suppressed in the solution-grown crystals, allowing the moments associated with the ${\mathrm{Eu}}^{2+}$ state to order antiferromagnetically at around 14 K. A detailed analysis of the crystal structure using single crystal x-ray diffraction reveals that, although the solution grown crystals are built from the same constituent layers as the arc-melted samples, these layers present a different stacking. The effect of different thermal treatments is also studied. Different anneal procedures did not result in significant changes in the intrinsic properties, and only by arc-melting and quenching the crystals we were able to convert them into the previously reported polymorph.

Close

PrevNext

View figure in article

• Crystal phenomena
• Magnetic order
• Magnetic phase transitions
• Crystal growth
• Mössbauer spectroscopy
• X-ray diffraction