Figure 4. Hyperfine parameters of the V_N⁻ spin.

Principal values (in MHz) of the hyperfine tensors and Fermi contact terms for interaction between the V_N⁻ electronic spin (S = 1) with the nearest four ²⁷Al nuclei as a function of the uniaxial (a–c) and biaxial (d–f) strains. The four ²⁷Al nuclei (Al₁ to Al₄) can be seen in Fig. 1. Note that the applied uniaxial strain and the biaxial strain are compressive (negative value) along the [] direction and tensile (positive value) in the (0001) plane, respectively. The local defect geometry of the S = 1 state changes from C_1h^(a1+e) to C_3v for biaxial strain larger than 2%, inducing the drastic change in the hyperfine parameters.