Kondo effect due to Cu substitution in the kagome compound La₂(Cu_xNi_1-x)₇

La₂Ni₇ is a small moment itinerant antiferromagnet with a saturated moment of ~ 0.1μ_B/Ni and a series of three AFM transitions at 61.0 K, 56.5 K, and 42.2 K [1], making it a favorable system to tune magnetic order towards quantum criticality. Application of hydrostatic pressure, however, indicated very little pressure dependence on the transition temperatures up to 2 GPa. On the other hand, we find that La₂Ni₇ is highly tunable by chemical substitution of Ni with adjacent Cu. Single crystals of La₂(Cu_xNi_1-x)₇ were synthesized, and detailed characterization was performed on them. For 0.00 ≤ x ≤ 0.097, both the transition temperatures as well as the saturated and effective moment are suppressed with Cu substitution. Increasing the Cu substitution level to 0.125 and higher, 0.125 ≤ x ≤ 0.177, shows anomalous behavior in resistivity and specific heat data, suggesting the existence of a Kondo-like behavior for these samples. The intermediate x = 0.105 lies in between the magnetic ordered and Kondo regimes in the vicinity of a possible QCP for this system and may exhibit NFL behavior. Although the results of all the Cu substituted samples will be discussed, more emphasis will be placed on the higher-doped ones.



[1] Ribeiro, R. A. et al., Phys Rev B 105, 014412 (2022).