Anisotropic magnetic coupling with a two-dimensional characteristic in noncentrosymmetric Cr₁₁Ge₁₉

In this work, we successfully synthesize the single crystal Cr₁₁Ge₁₉. The magnetism of the noncentrosymmetric Cr₁₁Ge₁₉ with itinerant ferromagnetic ground state is thoroughly investigated on the single crystal. Based on the variation measurements including the angular rotation, temperature, and magnetic field dependence of magnetization, we find that this material exhibits strong magnetic anisotropy along the c-axis. To clearly reveal the magnetic interactions, the critical behavior is studied using the modified Arrott plot, the Kouvel-Fisher method, and the critical isotherm technique. Combining these different methods, three main critical exponents (β, γ, and δ) are obtained. The critical exponent β is close to the theoretical prediction of a three-dimensional XY model with spin-dimensionality n = 2, indicating two-dimensional magnetic coupling. Meanwhile, the critical exponent γ suggests that the magnetic interaction is of long-range type with magnetic exchange distance decaying as J(r) ≈ r^-4.61. We propose that the ferromagnetic ground state of Cr₁₁Ge₁₉ is formed by the polarized magnetic moments along the c-axis, while the long-range magnetic coupling is established within the ab plane.