Specific features of the anisotropy of low-temperature microwave magnetoresistivity of lightly doped $p$-Ge due to the presence of light and heavy holes

The microwave magnetoresistivity of lightly doped (nondegenerate) $p$-Ge has been studied by the electron spin resonance method. This technique can be employed to record the derivative of the microwave absorption with respect to the magnetic field on the assumption that changes in this absorption are proportional to changes in the conductivity of a semiconductor. At the 10-GHz frequency of the electromagnetic field, the averaging time of the effective masses of light and heavy holes at low temperatures is substantially longer than the oscillation period. This makes it possible to study the individual responses of light and heavy holes to the magnetic field. It is shown that the microwave magnetoabsorption associated with light holes only slightly depends on the direction of the magnetic field relative to the crystallographic axes of Ge. At the same time, the signal related to heavy holes changes by several times when a sample is rotated in a magnetic field. The experimental results are correlated with the theory of the classical magnetoresistive effect.