Investigation of the physical properties of the Ce2MAl7Ge4 (M = Co, Ir, Ni, Pd) heavy fermion compounds

Nirmal J. Ghimire; S. K. Cary; S. Eley; N. A. Wakeham; P. F. S. Rosa; T. Albrecht-Schmitt; Y. Lee; M. Janoschek; C. M. Brown; L. Civile; J. D. Thompson; F. Ronning; E. D. Bauer

doi:10.1103/PhysRevB.93.205141

paper

Investigation of the physical properties of the Ce2MAl7Ge4 (M = Co, Ir, Ni, Pd) heavy fermion compounds

arXiv:1604.07927 · doi:10.1103/PhysRevB.93.205141

Abstract

We report the synthesis, crystal structure and characterization by means of single crystal x-ray diffraction, neutron powder diffraction, magnetic, thermal and transport measurements of the new heavy fermion compounds Ce $_{2}$ MAl $_{7}$ Ge $_{4}$ (M = Co, Ir, Ni, Pd). These compounds crystallize in a noncentrosymmetic tetragonal space group P\={4}2 $_{1}$ m, consisting of layers of square nets of Ce atoms separated by Ge-Al and M-Al-Ge blocks. Ce $_{2}$ CoAl $_{7}$ Ge $_{4}$ , Ce $_{2}$ IrAl $_{7}$ Ge $_{4}$ and Ce $_{2}$ NiAl $_{7}$ Ge $_{4}$ order magnetically behavior below $T_{M} =$ 1.8, 1.6, and 0.8 K, respectively. There is no evidence of magnetic ordering in Ce $_{2}$ PdAl $_{7}$ Ge $_{4}$ down to 0.4 K. The small amount of entropy released in the magnetic state of Ce $_{2}$ MAl $_{7}$ Ge $_{4}$ (M = Co, Ir, Ni) and the reduced specific heat jump at $T_{M}$ suggest a strong Kondo interaction in these materials. Ce $_{2}$ PdAl $_{7}$ Ge $_{4}$ shows non-Fermi liquid behavior, possibly due to the presence of a nearby quantum critical point.

To appear in Phys. Rev. B