Ammonium dihydrogen phosphate (ADP) crystals have been grown in the presence of various concentrations (1, 5 and 10 mol%) of cadmium(II) salt by slow evaporation of saturated solution method. The concentration of the incorporated Cd2+ ion has been determined by energy-dispersive X-ray spectrometry. The surface nature of the as-grown crystals has been analysed by scanning electron microscopic studies. Presence of Cd2+ in the crystal lattice of ADP has not altered the basic structure of ADP as evidenced by powder X-ray diffraction and single-crystal X-ray diffraction analyses. Thermogravimetry and differential thermal analyses of the samples reveal that there is no physically adsorbed water molecule in the pure and doped specimens. The grown crystals were also characterized by FT-IR, UV–Vis and diffuse reflectance spectra. It is interesting to observe the second harmonic generation efficiency, a nonlinear optical property estimated by Kurtz powder technique has been increased when compared to the pure ADP up to the moderate concentration of cadmium.

We have prepared pure and divalent vanadyl ion-doped magnesium rubidium sulfate hexahydrate crystals by using slow evaporation solution growth technique. It is interesting to observe that Vo(II) doping influences the physical properties of MRSH. Presence of Vo(II) ions in the doped specimen was confirmed by energy dispersive spectroscopy and electron paramagnetic resonance spectroscopy. FTIR studies reveal that the doping of vanadium ion has not altered the basic structure of MRSH. Scanning electron microscope studies of doped sample reveals that structure defect centers are formed in the crystals. Gradual decomposition patterns were observed for pure and doped specimens in thermogravimetry and differential thermogravimetry. The grown crystals were also characterized by powder X-ray diffraction. The second harmonic generation efficiency tested using Kurtz powder technique is not influenced by the added dopant.

Single crystals of pure and cupric ion (Cu(II))-doped magnesium rubidium sulfate hexahydrate (MRSH) were prepared by slow evaporation of saturated solution technique (SEST) and the influence of dopant Cu(II) on the MRSH crystals has been investigated. Incorporation of Cu(II) into the crystalline matrix was confirmed by energy dispersive spectroscopy (EDS) and electron paramagnetic resonance (EPR) spectroscopy. Thermogravimetric (TG) analysis of the doped sample reveals the faster rate of degradation. EPR spectrum of the MRSH both at room temperature and at 77 K indicates the presence of Cu(II) in the interstitial position. The grown crystals were also characterized by UV–VIS and IR spectroscopy. The surface morphology of the doped sample studied by scanning electron microscopy (SEM) indicates different morphology at various magnifications. The non-linear optical (NLO) property measured using second harmonic generation (SHG) efficiency test reveals that the non-linearity is not facilitated by doping of Cu(II).

In order to understand the effect of charge compensating vacancies on the number, orientation and magnitude of D-tensors, single crystal EPR measurements have been carried out with Cr(III) in zinc(II) potassium phosphate hexahydrate at room temperature. During crystal rotations, a maximum of 6/7 resonance lines or a minimum of 2 is noticed. Crystal rotations done in the three orthogonal planes have yielded spin Hamiltonian parameters for one site with: g(xx)=1.969, g(yy)=1.995, g(zz)=2.107; D-xx=66.2 mT; D-yy=91.7 mT, and D-zz=-157.9 mT. The powder EPR spectrum indicates a very broad line at g = 8, without any extra resonances from 0 to 650 mT both at room temperature and 77 K. The reason may be that due to large zero field splitting, the resonance at g = 2 is shifted to g = 8 position and the other resonances are below 0 or above 650 mT. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Single crystal electron paramagnetic resonance (EPR) studies of Mn(II) doped zinc potassium phosphate hexahydrate have been carried out at room temperature. Single crystal rotations along the three orthogonal axes indicate orthorhombic symmetry with spin-Hamiltonian parameters as: g(xx) = 1.9997; g(yy) = 1.9538; g(zz) = 1.9524, D(xx) = 15.49 mT; D(yy) = 0.22 mT; D(zz) = -15.71 mT, A(xx) = 11.70 mT; A(yy) = 10.53 mT; A(zz) = 10.42 mT and a = 0.8 x 10(-4) cm(-1). A large E term indicates considerable distortion from axial symmetry. The impurity is found to enter the lattice substitutionally. The distortion axis for the impurity has been identified along one of the Zn-O bond directions in the crystal.

Single crystal EPR studies of Mn(II)-doped zinc ammonium phosphate hexahydrate (ZnNH4PC4·6H2O) have been reinvestigated at room temperature. Single crystal rotations along the three orthogonal axes indicate that the spin Hamiltonian parameters for the interstitial site are:g xx = 1.966,g yy = 1.972,g zz = 1.976;D xx = -12.28 mT,D yy = -2.09 mT andD zz = 14.37 mT;A xx = 9.06 mT,A yy = 9.06 mT andA zz = 11.09 mT;a = -0.11 mT. These parameters differ considerably from the previous report of Chand and Agarwal and indicate the orthorhombic nature of the paramagnetic impurity. The impurity is found to enter the lattice interstitially, in contrast to earlier prediction of substitutional position. The percentage covalency of the Mn-0 bond has been estimated.

Single crystal EPR studies of VO(II)-doped magnesium potassium Tutton's salt have been carried out at room temperature. The results indicate that the paramagnetic impurity has entered the lattice, both substitutionally and interstitially and the maximum hyperfine for the substitutional site along the a axis corresponds to the minimum hyperfine for interstitial site and vice versa. The spin Hamiltonian parameters obtained from single crystal data for these sites are: Site 1, gparallel = 1.954(1); gperpendicular = 1.998(1), Aparallel = 19.80(2) mT; Aperpendicular = 7.61(2) mT; Site 2, gparallel = 1.997(1); gperpendicular = 1.952(1), Aparallel = 7.66(2) mT; Aperpendicular = 19.85(2) mT. Superhyperfine from ligand protons have been observed at certain orientations for Site 2 impurity. Powder spectrum shows a set of eight parallel and perpendicular features indicating the presence of only one site and these values matched with Site 1 values. From these observations, it has been concluded that the two vanadyl impurities are approximately at right angles to each other. Cooling the sample to 77 K does not change the spectra appreciably. The admixture coefficients have been calculated from Site 1 data, which agree well with the reported values.