Exchange interaction effect on oscillatory magnetoresistance in n-type Hg1-x-yCdxMnyTe near semimetal-semiconductor transition

Shubnikov-de Haas oscillations of magnetoresistance are studied in semimagn etic quaternary solid solutions of n-Hg1-x-yCdxMnyTe (x < 0.230, y <less th an or equal to> 0.022) with a small positive energy gap E-g (E-g less than or equal to 120 meV). The data show that the exchange interaction constant cr for magnetic coupling between the free carrier spin and localized magnet ic moments of manganese ions is smaller (alphaN(0) approximate to 0.3 eV) f or compounds with E-g < 50 meV in comparison with that (<alpha>N-0 = 0.45 e V) determined from magnetoresistance and magnetoluminescence data for solut ions with E-g > 100 meV. The effect of the or value reduction is found to b e the most pronounced near the semimetal-serniconductor transition and prob ably depends on the value of spin-orbit splitting in semimagnetic semicondu ctors. It is assumed to be connected with the growth of p-d exchange admiri ng due to the small E-g value.