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TT: Fachverband Tiefe Temperaturen

TT 52: Heavy Fermions

TT 52.3: Vortrag

Mittwoch, 11. März 2026, 15:30–15:45, HSZ/0103

Pressure evolution of coplanar antiferromagnetism in heavy-fermion Ce₂CoAl₇Ge₄ — •Mukkattu O. Ajeesh^1,2, Allen O. Scheie¹, Yu Liu¹, Lucas Keller³, Sean M. Thomas¹, Priscila F. S. Rosa¹, and Eric D. Bauer¹ — ¹Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA — ²Department of Physics, Indian Institute of Technology Palakkad, Kerala 678623, India — ³Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, Villigen CH-5232, Switzerland

Ce₂MAl₇Ge₄ (M = Co, Ir, Ni, or Pd) compounds are heavy-fermion materials that exhibit a variety of ground states ranging from magnetism to non-Fermi-liquid behavior. The Co, Ir, and Ni members undergo magnetic ordering with decreasing transition temperatures across the series. In contrast, the Pd compound shows no magnetic order down to 0.4 K and exhibits non-Fermi-liquid behavior, indicating proximity to a magnetic quantum critical point. Among these materials, Ce₂CoAl₇Ge₄ orders antiferromagnetically below T_N = 1.9 K and displays heavy-fermion behavior below 15 K. We investigated the magnetic structure of its antiferromagnetic phase along with the evolution of the magnetic transition under external pressure. Resistivity and ac calorimetry measurements under hydrostatic pressure reveal that T_N is suppressed to 1 K at p≈1 GPa, above which the transition abruptly disappears in a first order-like fashion. These results highlight that transition metal substitution is not merely a lattice volume effect akin to applied pressure; instead, carrier doping and anisotropic changes in lattice parameters likely play important role.

Keywords: Heavy-Fermion antiferromagnet; Quantum phase transition; Pressure tuning; Magnetic structure