Physical properties of $R$Co${}_2$Al${}_8$ ($R=$ La, Ce, Pr, Nd and Sm) single crystals: An emerging structure-type for anisotropic Kondo lattice studies

Abstract

Systematic investigations of rare-earth ($R$) based intermetallic materials are a leading strategy to reveal the underlying mechanisms governing a range of physical phenomena, such as the formation of a Kondo lattice and competing electronic and magnetic anisotropies. In this work, the magnetic, thermal and transport properties of $R$Co${}_2$Al${}_8$ ($R=$ La, Ce, Pr, Nd and Sm) single crystals are presented. LaCo${}_2$Al${}_8$ is characterized as a Pauli paramagnet and transport measurements, with the current along and perpendicular to the orthorhombic $c$-axis (${\rho }_c$ and ${\rho }_{ab}$, respectively), reveal a clear electronic anisotropy, with ${\rho }_{ab}\approx (4-7){\rho }_c$ at $300$ K. We show that CeCo${}_2$Al${}_8$ is a Kondo-lattice for which the Kondo coherence temperature $T_{\text{K}}^{\ast }$, deduced from broad maximums in ${\rho }_c$ and ${\rho }_{ab}$ at $\approx$ 68 and 46 K, respectively, is also anisotropic. This finding is related to a possible underlying anisotropy of the Kondo coupling in CeCo${}_2$Al${}_8$. The Pr- and Nd-based materials present strong easy-axis anisotropy ($c$-axis) and antiferromagnetic (AFM) orders below $T=4.84$ K and $T=8.1$ K, respectively. Metamagnetic transitions from this AFM to a spin-polarized paramagnetic phase state are investigated by isothermal magnetization measurements. The Sm-based compound is also an easy-axis AFM with a transition at $T=21.6$ K.

13 pages, 8 figures, published in Phys. Rev. B

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• Quantum criticality
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• Kondo-lattice ferromagnets and their peculiar order along the magnetically hard axis
• Realization of Kondo chain in CeCo${}_2$Ga${}_8$
• Pr-magnetism in the quasi-skutterudite compound PrFe${}_2$Al${}_8$

Cited by in corpus (1)

• Stability Frontiers and Mixed-dimensional physics in the Kagome Intermetallics Ln3ScBi5 (Ln = La-Nd, Sm)