Very-narrow-gap bulk-grown HgCdTe single crystals are multicarrier semiconductor system material, since the multiple electrons and holes species frequently contribute to the conduction. Especially for the slight p-type HgCdTe single crystals, the conventional measurements of a single magnetic field can lead to erroneous conclusions because of the large ratio of the electron mobility to hole mobility. The n-type crystals with poor mobility and slight p-type crystals with excellent electrical properties cannot be distinguished by the conventional single-field data. Variable-magnetic-field Hall measurements are performed on bulk-grown HgCdTe single crystals at various temperatures. From the results, the variable-magnetic-field Hall measurements are found to be a suitable tool for differentiation electrical characterization of the two type HgCdTe single crystals. The operating principle of the trapping-mode photoconductive HgCdTe detectors is investigated.