Unconventional magnetic order emerging from competing energy scales in the new RRh₃Si₇ intermetallics (R = Gd-Yb)

The competition between Ruderman-Kittel-Kasuya-Yosida (RKKY), crystal electric field (CEF), and Kondo energy scales is known to give rise to complex magnetism in many rare earth-based intermetallics. In this talk I will focus on the hard axis magnetic ordering, where the magnetic moment orders along the hard CEF axis, in the RRh₃Si₇ series of compounds (R = Gd - Yb). We compare the influence of each energy scale on the magnetic order, by studying the members with only RKKY interactions (R = Gd), both RKKY and CEF effects (R = Tb-Tm), and with all three interactions (R = Yb). Beyond the RRh₃Si₇ series , we extended the comparison to other isostructural Kondo systems, YbIr₃Si₇ [1] and YbIr₃Ge₇ [2], where the hard axis magnetic order is also observed. We find that the non-Kondo RRh₃Si₇ compounds do not show the hard axis magnetic order, while this does occur in all three Kondo systems YbRh₃Si₇, YbIr₃Si₇ and YbIr₃Ge₇, suggesting the crucial role of Kondo effect in hard axis magnetic ordering. Aside from Kondo effect, the CEF-RKKY competition causes complex magnetic ground states, showing entangled magnetic and electronic degrees of freedom in all compounds of the family.

[1] arXiv:1908.11336, 2019

[2] Phys. Rev. B 99, 121109(R), 2019