Ferromagnetic quantum criticality and strange metal behavior in doped CeRh₆Ge₄

The recent discovery of a pressure-induced ferromagnetic (FM) quantum critical point (QCP) and strange metal behavior in the heavy fermion metal CeRh6Ge4 [1] has attracted considerable interests. To further investigate the origin of FM QCP and its related properties, we recently performed a series of studies on the doped CeRh6Ge4. The ferromagnetic transition can be effectively suppressed by elemental substitutions at different sites. However, the critical behavior of electrical resistivity strongly depends on the site substitutions. While the T-linear resistivity is largely interfered by the enhanced disorder for the substitutions at the Ce- and Ge-sites [2,3], it remains unchanged at a critical Rh-site substitution [4], being similar to the case of pressure tuning. On the other hand, the logarithmic temperature dependence of the electronic specific heat at the critical point is robust against disorder for all the site substitutions [4]. Furthermore, a power-law behavior of the Grüneisen ratio is observed at the critical point, suggesting unconventional nature of the FM QCP.



[1] B. Shen, Yongjun Zhang, Yashar Komijani, Michael Nicklas, Robert Borth, An Wang, Ye Chen, Zhiyong Nie, Rui Li, Xin Lu, Hanoh Lee, Michael Smidman, Frank Steglich, Piers Coleman, Huiqiu Yuan, Strange-metal behaviour in a pure ferromagnetic Kondo lattice, Nature 579, 51 (2020).

[2] Jia-Cheng Xu, Hang Su, Rohit Kumar, Shuai-Shuai Luo, Zhi-Yong Nie, An Wang, Feng Du, Rui Li, Michael Smidman, and Hui-Qiu Yuan*, Ce-Site Dilution in the Ferromagnetic Kondo Lattice CeRh₆Ge_4, Chinese Phys. Lett. 38, 087101 (2021).

[3] Y. J. Zhang, Z. Y. Nie, R. Li, Y. C. Li, D. L. Yang, B. Shen, Y. Chen, F. Du, S. S. Luo, H. Su, R. Shi, S. Y. Wang, M. Nicklas, F. Steglich, M. Smidman*, and H. Q. Yuan*, Suppression of ferromagnetism and influence of disorder in silicon-substituted CeRh6Ge4, Phys. Rev. B 106, 054409 (2022).

[4] H. Q. Yuan et al., unpublished