Electron-nuclear double-resonance study of Mn2+ ions in ZnGeP2 crystals -: art. no. 033202

Electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) have been used to characterize isolated Mn2+ (3d(5)) ions in a bulk ZnGeP2 crystal grown by the horizontal Bridgman technique. From the EPR data, we obtain g(parallel to)=2.0019, g(perpendicular to)=2.0016, D=-211.7 MHz, a=27.6 MHz, and F=2.3 MHz. The two equivalent sites occupied by the Mn2+ ions are related by a "twist" angle of 5.6 degrees (this angle describes the small clockwise and counterclockwise rotations of the MnP4 units about the unique [001] crystal axis). ENDOR signals from the Mn-55 nuclei give A(parallel to)=-156.59 MHz, A(perpendicular to)=-157.90 MHz, and P=0.312 MHz for the hyperfine and nuclear electric quadrupole parameters, respectively. Principal values and principal-axis directions for three sets of neighboring P-31 nuclei are also obtained from ENDOR spectra. These principal values are A(parallel to)=5.30 MHz and A(perpendicular to)=4.09 MHz for one set, A(parallel to)=5.04 MHz and A(perpendicular to)=3.29 MHz for the second set, and A(parallel to)=3.16 MHz and A(perpendicular to)=1.19 MHz for the third set.