The magnetization process of the S = 1/2 Kondo necklace spin chain with the anisotropic ferromagnetic interaction is investigated using the numerical diagonalization of finite-size systems. As a result, it is found that the two-magnon bound state appears in the field-induced Tomonaga-Luttinger liquid phase for sufficiently large anisotropy. The critical exponent analysis indicates that the spin nematic correlation is dominant at higher magnetization region in the two-magnon bound phase. The phase diagram with respect to the anisotropy and the magnetization is presented.
Hasegawa et al. (2026) studied this question.