Substitution of 4d magnetic ions of a Kitaev-Heisenberg magnet by 3d magnetic ions: the case of Ru_1-xCr_xCl₃

The J_eff=1/2 Mott insulator alpha-RuCl₃ is a promising candidate for the realization of the Kitaev-Heisenberg model. It harbors an antiferromagnetic ground state below T_N=7K, however, this ordered state can be suppressed by a magnetic field through a quantum critical point toward a possible quantum spin liquid [1]. In this study, the Ru³⁺ ions with J_eff=1/2 moments were partially substituted by Cr³⁺ ions with S=3/2. The effect of this substitution on the magnetic interactions, the magnetic ground state and the field-induced quantum spin liquid were studied by means of magnetization, ac susceptibility and specific heat measurements. The ground state of Ru_1-xCr_xCl₃ was found to be a spin glass on a broad Cr concentration range with a maximum of the freezing temperature around x=0.5. Moreover, the evolution of the magnetic anisotropy with the substitution reveals a rather complex nature of the magnetic interaction between the Ru and Cr magnetic moments.

[1] S.-H. Baek, S.-H. Do, K.-Y. Choi, Y. S. Kwon, A. U. B.Wolter, S. Nishimoto, J. van den Brink, and B. Büchner, Phys. Rev. Lett. 119, 037201 (2017).