Crystallographic and magnetic descriptions of a novel erbium rich aluminide: Er10Co1+xAl3−x (x = 0.30)
Graphical abstract
Introduction
Erbium-based intermetallics can exhibit remarkable physical properties such as superconductivity [1], [2], hard magnetic properties [3], elevated thermopower [4] or important magnetocaloric effect (MCE). This is the case for the Er-rich compounds Er3Ni2[5], Er3Ir [6] or Er3Co [7], [8] presenting interesting MCE features at low temperature. Such behaviors motivated us to investigate some ternary Er–T–X (T = transition metal; X = p-block element) systems (e.g. Er–Cu–Ga [9], [10] or Er–Fe–Al [11]) in order to discover new phases with original properties. The Er–Co–Al system, where, to the best of the author's knowledge, two ternary phases only – ErCo1+xAl1−x (from paramagnetic to ferromagnetic, depending on the value of x) [12] and Er2Co3Al9 (ferromagnet below TC = 5 K) [13] - are reported, is a good candidate for such investigations.
In the present paper, we report on the crystallographic and magnetic properties of a novel ternary aluminide, namely Er10Co1+xAl3−x, discovered in the Er–Co–Al system. Its original structure-type is discussed versus closely related ones.
Section snippets
Experimental details
The samples were prepared by arc-melting the constitutional elements (all purities above 99.9 wt.%) in an arc-furnace under a protective Ti–Zr gettered argon atmosphere. To ensure good homogeneity, they were turned over and re-melted two times. Heat treatments were carried out in Ar-cleaned evacuated silica tubes, with all ingots first placed in alumina crucibles. Annealings were performed in electrical resistance furnaces at 1123 K for one week, followed by water-quenching of the tubes.
Phase formation
A ternary phase with approximate composition Er70(1)Co9(1)Al21(1) (the compositions are given in at.% throughout the paper) was first observed on SEM-EDS experiments on erbium rich samples of the Er–Co–Al ternary system annealed at 973 or 1123 K. Any attempt to index the corresponding powder XRD patterns using known binary phases from the Er–Co and Er–Al boundaries or ternary rare earth rich intermetallic phases failed, indicating the existence of a novel phase with this composition. Single
Conclusion
A novel erbium rich ternary intermetallic compound, Er10Co1+xAl3−x (x = 0) has been discovered in the Er–Co–Al ternary system. Single crystal X-ray diffraction reveals that it crystallizes in a hexagonal ordered variant of the Co2Al5-type where substitutions occur between Co1 and Al1 on the one hand and Er3 and Er4 on the other hand.
The magnetic behaviour is dominated by an antiferromagnetic ordering observed at TN = 12.7(7) K but a more complex order is envisaged to explain the upturn in χ(T)
Acknowledgements
This work has been supported by a bilateral CNRS-DGRS bilateral exchange program between France and Tunisia.
The authors are grateful to Francis Gouttefangeas (Centre de Microscopie Électronique à Balayage et microAnalyse, Université Rennes 1) for SEM-EDS analyses and Thierry Guizouarn (Institut des Sciences Chimiques de Rennes) for magnetic measurements.
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