Peculiarities of the exchange interaction in narrow-gap Hg1-x-yCdxMnySe

The peculiarities of the exchange interaction between the carrier spin and localized spin moments of magnetic ions near the semimetal-semiconductor transition have been studied in a semimagnetic quaternary solid solution system, Hg1-x-yCdxMnySe (x = 0.10, y = 0.02, E-g = 45 meV), by means of Shubnikov-de Haas oscillations. The measurements show that the exchange 'constant' alpha is actually a somewhat complicated function <(alpha)over tilde> of energy gap E-g and electron concentration, which changes from negative values (<(alpha)over tilde>N-0 = -0.15 eV) at lower electron concentration to positive values (<(alpha)over tilde>N-0 = 0.28 eV) at higher electron concentration, values which are more typically associated with wide-gap semimagnetic semiconductors.