Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 5: f-Electron Systems and Heavy Fermions I

TT 5.10: Vortrag

Montag, 12. März 2018, 12:15–12:30, H 3005

Nuclear magnetic resonance investigation of the novel heavy fermion system Ce₂CoAl₇Ge₄ — •Adam P. Dioguardi^1,2, Pedro Guzman^2,3, Priscila F. S. Rosa², Nirmal J. Ghimire², Serena Eley², Stuart E. Brown³, Joe D. Thompson², Eric D. Bauer², and Filip Ronning² — ¹IFW Dresden, Institute for Solid State Research, P.O. Box 270116, D-01171 Dresden, Germany — ²Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA — ³Department of Physics and Astronomy, UCLA, Los Angeles, California 90095, USA

We present nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements performed on single crystalline Ce₂CoAl₇Ge₄, a member of a recently discovered family of heavy fermion materials Ce₂MAl₇Ge₄ (M = Co, Ir, Ni, or Pd). A clear Knight shift anomaly (K ¬∝χ) is observed at coherence temperatures T^* ∼ 17.5 K for H₀ ∥ ĉ and 10 K for H₀ ∥ â at the ⁵⁹Co site, and T^* ∼ 12.5 K at the ²⁷Al(3) site for H₀ ∥ â characteristic of the heavy fermion nature of this compound. At high temperatures the ⁵⁹Co NMR spin-lattice relaxation rate T₁⁻¹ is dominated by spin fluctuations of the 4-f local moments with a weak metallic background. Furthermore, we find (T₁TK)⁻¹ ∝ T^−1/2 at the ⁵⁹Co site as expected for a Kondo system for T < T^* and T < T_K. ⁵⁹Co NQR T₁⁻¹ measurements at low temperatures indicate slowing down of spin fluctuations above the magnetic ordering temperature T_M ∼ 1.8 K. A weak ferromagnetic character of fluctuations around q=0 is evidenced by an increase of χ T vs T above the magnetic ordering temperature.