Indirect Spin–Spin Coupling in InP Investigated by Triple-Resonance NMR under Magic-Angle Spinning

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The ³¹P NMR spectra were measured using ³¹P, ¹¹³In and ¹¹⁵In triple-resonance and magic-angle spinning (MAS) to investigate an indirect spin–spin interaction in undoped and Fe-doped InP semiconductors. The linewidth of the static NMR spectrum obtained by cross polarization (CP) of ¹¹⁵In→³¹P with ¹¹⁵In decoupling was explained by the lattice sum of ³¹P–³¹P dipolar couplings. On the other hand, the linewidth of the MAS NMR spectrum obtained by CP of ¹¹⁵In→³¹P without ¹¹⁵In decoupling was interpreted by the isotropic indirect interaction of neighboring ¹¹⁵In–³¹P spins. We obtained 10 equally spaced lines corresponding to ¹¹³In spin state from the MAS NMR spectrum measured with CP from rare ¹¹³In to ³¹P under ¹¹⁵In decoupling. From these experiments, the isotropic contributions of the electron-mediated nuclear coupling between the nearest neighboring ^113,115In–³¹P spins was obtained as |¹J^iso(I,S)|=224±5 Hz for undoped and Fe-doped InP samples. The ¹J^iso(I,S) value was found to be unaffected by the carrier with the density in the range of 10⁷–10¹⁵ cm⁻³.