Effect of nonparabolicity on the conduction-electron spin resonance in cubic semiconductors

The spin-resonance amplitude of conduction electrons in a cubic crystal has been calculated keeping terms up to fourth order in the wave vector k in the 2×{}2 effective-mass Hamiltonian. Apart from corrections to the magnetic dipole amplitude, we find that the terms γ₀{{μ}}B$(${{σ}}ₓB₀ₓ{k}ₓ²$ +${{σ}}yB0y{k}y²$+${{σ}}zB0z{k}z²$) and g''${{μ}}Bσ·k,{B}₀·k yield electric dipole amplitudes proportional to k·{B}₀$. While in the ordinary Voigt and cyclotron-resonance-active Faraday configurations only the ${{γ}}₀$ term is effective, in the cyclotron-resonance-inactive Faraday configuration both the ${{γ}}₀$ and g'' terms contribute. We have calculated the angular dependence of the ${{γ}}₀$ amplitude for arbitrary crystal orientations, the g'' amplitude being isotropic. In narrow-band-gap materials the admixture of hole states into the electron eigenstates also contributes an isotropic electric dipole spin-flip amplitude proportional to k{·}B₀, which is distinct from those mentioned.