Electron paramagnetic resonance and electron-nuclear double resonance study of Mn2+ ions in CdGeAs2 crystals

Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) have been used to characterize Mn2+ (3d(5)) ions in CdGeAs2 crystals grown by the horizontal Bridgman method. These samples were p-type with room-temperature hole concentrations ranging from 2 x 10(15) cm(-3) to 5 x 10(16) cm(-3). The Mn2+ ions substitute for the Cd2+ ions in this tetragonal chalcopyrite lattice, and form "deep" isoelectronic centers. Their g values and crystal-field parameters are g(parallel to) = 2.0025, g(perpendicular to) = 2.0011, D = 118.8 MHz, a + 2/3F = 18.4 MHz, and a = -0.3 MHz. The hyperfine and nuclear electric quadrupole parameters for the Mn-55 nucleus are A(parallel to) = -154.94 MHz, A(perpendicular to) = =155.69 MHz, and P = 0.622 MHz. Hyperfine parameters for one set of nearby Cd nuclei and two sets of nearby As nuclei were also determined using ENDOR. No evidence was found in these doped bulk crystals to suggest that Mn4+ ions substitute for Ge4+ ions. (C) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.