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

Abstract

We report the synthesis, crystal structure, and characterization by means of single-crystal x-ray diffraction, neutron powder diffraction, and magnetic, thermal, and transport measurements of the new heavy-fermion compounds Ce2MAl7Ge4 (M = Co, Ir, Ni, Pd). These compounds crystallize in a noncentrosymmetric tetragonal space group P (4) over bar2(1)m, consisting of layers of square nets of Ce atoms separated by Ge-Al and M-Al-Ge blocks. Ce2CoAl7Ge4, Ce2IrAl7Ge4, and Ce2NiAl7Ge4 order magnetically below T-M = 1.8, 1.6, and 0.8 K, respectively. There is no evidence of magnetic ordering in Ce2PdAl7Ge4 down to 0.4 K. The small amount of entropy released in the magnetic state of Ce2MAl7Ge4 (M = Co, Ir, Ni) and the reduced specific heat jump at TM suggest a strong Kondo interaction in these materials. Ce2PdAl7Ge4 shows non-Fermi liquid behavior, possibly due to the presence of a nearby quantum critical point. ©2016 American Physical Society