Competition of anisotropies in antiferromagnetic Ni3–xCoxB2O6 solid solutions

https://doi.org/10.1016/j.jpcs.2025.113452

In Ni_3–xCo_xB₂O₆ the direction of the easy axis of magnetization changes from the crystallographic direction c to the crystallographic direction b with an increasing concentration of cobalt ions due to the competition of anisotropies and exchange interactions. The theoretical calculations of the orientation of magnetic moments in the Ni_3–xCo_xB₂O₆ solid solutions are in good qualitative agreement with the experimental data. The orientation of magnetic moments is significantly influenced by the spin-orbit interaction of nickel and cobalt ions. In the Ni_2.81Co_0.19B₂O₆ compound two magnetic phase transitions are observed. Moreover, an oblique phase is observed in the concentration range 0.6 < x < 0.93.