Kliemt, K.; Banda, J.; Khanenko, P.; Scherzad, A.; Stockert, U.; Efimenko, A.; Kummer, K.; Krellner, C.; Brando, M.: Physical properties of the ferromagnetic quantum critical system YbNi4(P1-xAsx)2. Physical Review B 111 (2025), p. 125114/1-14
10.1103/physrevb.111.125114
Abstract:
We report on single-crystal growth and physical properties of the quantum critical Kondo-lattice system YbNi4(P1−𝑥As𝑥)2 with 0≤𝑥≤1 which hosts a ferromagnetic quantum critical point at 𝑥≈0.1 . We performed measurements of the magnetization, electrical resistivity, thermopower, heat capacity, and resonant x-ray emission spectroscopy. Arsenic substitution leads to a homogeneous increase of the unit-cell volume, with well-defined As concentrations in large parts of the single crystals. All data consistently show that with increasing 𝑥 the Kondo temperature increases, while the magnetic anisotropy observed at low 𝑥 fully vanishes toward 𝑥=1 . Consequently, at low temperatures, the system shows a crossover from pronounced non-Fermi liquid behavior for 𝑥≤0.2 to a Fermi liquid behavior for 𝑥>0.2 with weak correlations. There is a continuous change in Yb valence from nearly trivalent at low 𝑥 to a slightly lower value for 𝑥=0.6 , which correlates with the Kondo temperature. Interestingly, specific heat measurements at very low temperatures show that 𝐶/𝑇 strongly increases toward lower 𝑇 for 𝑥=0.13 and 𝑥=0.2 with a very similar power law. This suggests that in YbNi4(P1−𝑥As𝑥)2 a quantum critical line rather than a quantum critical point might exist.