Iron-Arsenic Associates in ZnSe

Electron paramagnetic resonance of ${\mathrm{Fe}}^{3+}$ in the strong trigonal field of a nearest-neighbor substitutional arsenic in ZnSe is reported. Superhyperfine structure is observed from the four nearest neighbors - one arsenic and three seleniums. The parameters appearing in an effective spin Hamiltonian with $S=\frac{1}{2}$ are $g_{\parallel }^e=2.\mathrm{}0238$, $g_{\perp }^e=6.\mathrm{}168$, $A\left({\mathrm{Fe}}^{57}\right)=6.\mathrm{}2\times {10}^{-4\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$, $B\left({\mathrm{Fe}}^{57}\right)=16.\mathrm{}8\times {10}^{-4\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$, $K_{\parallel }\left({\mathrm{As}}^{75}\right)=8.\mathrm{}71\times {10}^{-4\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$, and $K_{\perp }\left({\mathrm{As}}^{75}\right)=16.\mathrm{}20\times {10}^{-4\mathrm{}}$ ${\mathrm{cm}}^{-1\mathrm{}}$.