Ferromagnetic ordering along the hard axis in the Kondo lattice YbIr 3 Ge 7

• Published in: Physical review. B 2019-03, Vol.99 (12), Article 121109
• Main Authors: Rai, Binod K., Stavinoha, Macy, Banda, J., Hafner, D., Benavides, Katherine A., Sokolov, D. A., Chan, Julia Y., Brando, M., Huang, C.-L., Morosan, E.
• Format: Article
• Language: English
• Subjects: Anisotropy; Antiferromagnetism; Crystallography; Curie temperature; Electric fields; Ferromagnetism; Heat exchange; Kondo temperature; Magnetic permeability; Magnetism; Phase transitions; Symmetry; Variations
• ISSN: 2469-9950; 2469-9969
• DOI: 10.1103/PhysRevB.99.121109

Ferromagnetic Kondo lattice compounds are far less common than their antiferromagnetic analogs. In this Rapid Communication, we report the discovery of a ferromagnetic Kondo lattice compound, YbIr 3 Ge 7 . As in almost all ferromagnetic Kondo lattice systems, YbIr 3 Ge 7 shows magnetic order with moments aligned orthogonal to the crystal electric field (CEF) easy axis. YbIr 3 Ge 7 is unique in that it is the only member of this class of compounds that crystallizes in a rhombohedral structure with a trigonal point symmetry of the magnetic site, and it lacks broken inversion symmetry at the local moment site. The ac magnetic susceptibility, magnetization, and specific heat measurements show that YbIr 3 Ge 7 has a Kondo temperature T K ≈ 14 K and a Curie temperature T C = 2.4 K . Ferromagnetic order occurs along the crystallographic [100] hard CEF axis despite the large CEF anisotropy of the ground-state Kramers doublet with a saturation moment along [001] almost four times larger than the one along [100]. This implies that a mechanism which considers the anisotropy in the exchange interaction to explain the hard-axis ordering is unlikely. On the other hand, the broad second-order phase transition at T C favors a fluctuation-induced mechanism.