The interpretation of g factor of the VO2+ ion doped in defferent single crystals is made using the Stevens model where the symmetry of the crystalline field is tetragonal. The bonding parameters K|| and K┴, choosing the different parametric angle β, are determined. The value of K┴ should be less than 0.048 in order to have a better fit to the experimental g values

Kripal, Ram

Kumar Yadav, Awadhesh

Misra, Sanjay

English

Scitech Research Journals

Boson Journal of Modern Physics (BJMP)                                                        ISSN: 2454-8413  Volume 3, Issue 1 available at www.scitecresearch.com/journals/index.php/bjmp                                                  208|                                             SCITECH                                                                         Volume 3, Issue 1 RESEARCH ORGANISATION                                      February 25, 2017   Boson Journal of Modern Physics www.scitecresearch.com Crystalline Field Effect on bonding Parameters of VO2+ Ion Ram Kripal1, Sanjay Misra2 and Awadhesh Kumar Yadav3 1, 2, 3Department of Physics, University of Allahabad, Allahabad, 211 002, India E-mail: 1ram_kripal2001@rediffmail.com; 2ssopam@gmail.com, 3aky.physics@gmail.com.  Abstract The interpretation of g factor of the VO2+ ion doped in defferent single crystals is made using the Stevens model where the symmetry of the crystalline field is tetragonal. The bonding parameters K|| and K┴, choosing the different parametric angle β, are determined. The value of K┴ should be less than 0.048 in order to have a better fit to the experimental g values. Keywords: Electron paramagnetic resonance; parametric angle; Bonding parameters.  Introduction   Electron paramagnetic resonance (EPR) provides a great deal of information about the magnetic properties of paramagnetic ion in different host lattices. This method also provides a detailed description of the ground state wave function of paramagnetic ions and enables one to understand the nature of the electric field symmetry produced by the ligands around the metal ion. VO2+ ion has only one electron, i.e., it has 3d1 configuration which allows paramagnetic resonance to be observed at ambient temperature. The VO2+ ion is the most stable cation among a few molecular paramagnetic transition metal ions which is used extensively as an impurity probe for electron paramagnetic resonance studies. The paramagnetic VO2+ ion in different host lattices is studied and reported [1–10].       On the basis of the theoretical analysis of the behavior of 3d1 single electron in VO2+ ion doped single crystals, the ground state wave function and nature of bonding are estimated with the help of EPR data. In the present investigation, the experimental g values are explained by the Stevens model of covalent bonding in the presence of tetragonal crystalline field. It is seen that a better fit of the experimental g factor is obtained by taking one of the bonding parameters less than 0.048.  1. Theoretical Aspect      When VO2+ ion is doped in a crystal lattice, it experiences crystal field of octahedral symmetry having tetragonal distortion due to ligands around the metal ion. For this the Hamiltonian can be written as [11],                           ℋ = 0424020244044 )5( OBOBOOB                             (1) where B4 is the magnitude of the octahedral field and other terms are the tetragonal distortions of second and fourth degree. We can take into account the tetragonal field in a potential in the form[12],                                   )(44444440440402202 YYrAYrAYrAV                         (2) where the first and second term incorporate the tetragonal component. The lower states and their energies are:  Boson Journal of Modern Physics (BJMP)                                                        ISSN: 2454-8413  Volume 3, Issue 1 available at www.scitecresearch.com/journals/index.php/bjmp                                                  209|                                            Doublet:                    )1|1(|21  Singlet:                      )2|2(|21  Energy:                      ca638141                       dca95126172                                                                    (3)      where      a = 022145Ar                      c = 04414/3 Ar                       d = 44414/3 Ar   Stevens [12] has shown that states 1|  and 1|  etc. do not exhibit a purely d-nature due to pi- bonding between d-electron and the surrounding p-electron of oxygen atoms. We have two lower states due to a combined effect of the tetragonal field (with negative ∆) and the spin – orbit interaction        1|   =  2/1|0|sin2/1|1|cos          1|  =  2/1|0|sin2/1|1|cos                                       (4) where                    11)2/1(22tan   1  is reduced spin orbit interaction. The expressions for g- factors are given below as                                     ||g =  22 cos)1(sin2 K                                   (5)                                   g   = 2sincossin22 K where K is defined as                                       K = <+1|Lz|+1>  and it is assumed that covalent bonding is isotropic. If we assume that bonding is anisotropic we can write                                       ||g =  2||2 cos)1(sin2 K                                   (6)                                   g   = 2sincossin22 K where                                           K║ = <+1|Lz|+1>   and K┴ = √2 <+1|Lx|+0> From above equations we can estimate the nature of bonding inVO2+ ion doped different lattices with the help of EPR data and parametric angle β.  2. Results & Discussion Boson Journal of Modern Physics (BJMP)                                                        ISSN: 2454-8413  Volume 3, Issue 1 available at www.scitecresearch.com/journals/index.php/bjmp                                                  210|                                                 The covalent bonding parameters K║ and K┴ were determined with the help of EPR data of VO2+ ion doped in different single crystals given in Table 1 [13, 14, 15]. The values of these parameters K║ and K┴ with the parametric angle β shown in Table 2 satisfy the experimental g values.  In the presence of tetragonal crystalline field the covalent bonding parameters are less than 1 as there is no shifting of doublet in t2g and higher doublet eg. The result shows that the value of one covalent bonding factor K┴ should be less than 0.048 in order to have a better fit to the experimental g value [12]. The covalency is inversely proportional to the g value [16] and the value of g║ depends on the K║. If K║ decreases, g║ increases and covalency decreases showing that, the character of the complex will be more ionic. g depends on the K┴ and is directly proportional to it. Hence, its value will increase if K┴ increases; giving different nature to the complex as far as bonding is concerned. Table 1 E PR parameters for VO2+ ion in selected crystal lattices with tetragonal symmetry  S.N   Crystal Lattices                                          EPR  Parameters                                                     g║             g┴                          A║          A┴         [Ref.]   1. Germanium Dioxide          GeO2 : VO2+                                 1.9290       1.9771                   175           68            [13]  2. Cesium Cadmium      Sulfate Hexahydrate    Cs2Cd(SO4)2.6H2O                           : VO2+                                            1.9210        1.9871                   177           70              [13] 3. Magnesium Ammonium     Sulphate Hexahydrate       Mg(NH4)2(SO4)2        .6H2O: VO2+                        1.9141    1.9790                       180           73             [13] 4. Ammonium Selenate       (NH4)2.SeO4: VO2+                        1.9220    1.9821                        187           73            [13] 5. Zinc Cesium Sulphate          Hexahydrate      ZnCs2(SO4)2.6H2O                                              : VO2+                                            1.9350    1.9861                        182           73             [13]                                                 6. Potassium Succinate                C4H4KO4: VO2+                          1.9261     1.9781                       178           69             [13]                                                                                                                                                    7. Zinc lactate trihydrate        Zn(C3H5O3)2·3H2O: VO2+    1.9236    1.9999                        197          90              [14] Boson Journal of Modern Physics (BJMP)                                                        ISSN: 2454-8413  Volume 3, Issue 1 available at www.scitecresearch.com/journals/index.php/bjmp                                                  211|                                             8. Zinc ammonium phosphate                                                                                                     hexahydrate       ZnNH4PO4·6H2O: VO2+                                                                                              [15]                  Site I                           1.9668    1.9867                        172           66                   Site II                          1.9698    1.9909                        149           57  Table 2. The value of covalent bonding Parameters (K║ & K┴) and the parametric angle β for VO2+ doped in some single crystals. S.N.  Crystal Lattices                      K║                            K┴                                          β          1.  Germanium Dioxide                                                        0.984                         0.002                                     96.31                                                               0.901                         0.004                                     96.40                                                        0.856                         0.006                                     96.45    2. Cesium Cadmium       Sulphate Hexahydrate                                                        0.953                         0.044                                      96.69                                                                 0.850                         0.046                                      96.81                                                        0.800                         0.048                                      96.87  3. Magnesium Ammonium      Sulphate Hexahydrate                                                         0.981                         0.023                                      96.91                                                                 0.961                         0.025                                      96.97                                                         0.853                         0.027                                      97.10 4. Ammonium Selenate                  0.966                         0.026                                      96.60                                                                  0.907                         0.028                                      96.70                                                          0.847                         0.030                                      96.77 5.  Zinc Cesium Sulphate        Hexahydrate                               0.924                         0.029                                      96.10                                                                   0.839                          0.031                                     96.19                                                          0.785                          0.032                                     96.25  6. Potassium Succinate  Boson Journal of Modern Physics (BJMP)                                                        ISSN: 2454-8413  Volume 3, Issue 1 available at www.scitecresearch.com/journals/index.php/bjmp                                                  212|                                                                                                    0.995                          0.009                                     96.45                                                             0.921                          0.011                                     96.51                                                         0.799                          0.014                                     96.65 7.  Zinc lactate trihydrate                                                         0.979                           0.031                                    96.10                                                                           0.970                           0.038                                    96.20                                                         0.963                           0.042                                    96.30  8. Zinc ammonium phosphate        hexahydrate                                                          Site I                                 0.937                          0.004                                      94.10                                                                                                                                                                 0.921                          0.008                                      94.20                                                          0.915                          0.012                                      94.30                 Site II                               0.980                          0.006                                      94.10                                                          0.943                          0.008                                      94.20                                                          0.811                          0.011                                      94.30   The rate of decrease of K║ is more than K┴ so that the compound can be approximately considered to be more ionic. Thus electron will migrate to neighboring atom suggesting that the net amount of charge transfer should also be considered in the crystal field theory of ionic complex. 3. Conclusion The nature of bonding of VO2+ ion doped in different single crystals has been evaluated. This result shows that the value of one covalent bonding parameter should be less than 0.048 in order to have a better fit to the experimental g value. The rate of decrease of K║ more than K┴ shows that the compound can be approximately considered more ionic. Acknowledgements The authors are thankful to the Head of Physics Department for providing departmental facilities. References [1] Yerli, Y. Zerenturk, A. Ozdogan, K. (2007). EPR of VO2+ in double formate, Ba2Zn(HCOO)6(H2O)4 single     Spectrochim. Acta A, 68 , 147-149. [2] Natarajan, B., Mithira, S., Deepa, S., Rao, P. S.  (2007).  EPR and optical investigation of VO(II) in    Zn(C3H3O4)2(H2O)2 single crystals: An interstitial site, J. Phys. Chem. Solids 68,1995-2002. [3] Karabulut, B., Tufan, A. (2006). An EPR and optical absorption study of VO2+ ions in sodium hydrogen oxalate monohydrate (NaHC2O4·H2O) single crystals Spectrochim. Acta A, 65, 742-748. [4] Velavan, K.,  Sougandi, I., Venkatesan, R., Rao,P. S. (2005). Observation of three sites for vanadyl in a   biomineral, zinc sodium phosphate hexahydrate: an EPR investigation , J. Phys. Chem. Solids 66, 15-20. [5] Deepa, S., Velavan, K.,  Sougandi, I.,  Venkatesan, R.,  Rao, P. S. (2005). Single crystal EPR study of VO(II) in  magnesium potassium phosphate hexahydrate: a case of two substitutional vanadyl ions,   Spectrochim. Acta A, 61, 2482-2487. [6] Gopal, N. O., Narasimhulu, K.V.,  Rao,  J. L. (2001).  EPR and optical absorption studies on VO2+ ions doped  in cobalt maleate tetrahydrate single crystals, Physica B 307, 117-124. Boson Journal of Modern Physics (BJMP)                                                        ISSN: 2454-8413  Volume 3, Issue 1 available at www.scitecresearch.com/journals/index.php/bjmp                                                  213|                                            [7] Shiyamala, C., Ranjendiran, T.M. (2002). Host Lattice Effect on Paramagnetic Impurity: Single Crystal EPR Study of   VO(II)-Doped Biomineral Cadmium Ammonium Phosphate Hexahydrate, Crys. Res. Technol. 37, 841-848. [8] Dhanuskodi, S., Jeyakumari, A. P. (2001). EPR studies of VO2+ ions in kainite single crystals, Spectrochim. Acta A, 57, 971-975. [9] Natarajan, B., Mithira, S., Deepa, S., Ravi Kumar, R.V.S.S.N., Rao, P. S. (2006). Identification of doped paramagnetic vanadyl impurity in dipotassium diaquabis (malonato-κ2O, O′) zincate dihydrate single crystal using EPR and optical techniques, Radiat. Eff. Defects Solids, 161, 177-187. [10] Tapramaz, R., Karabulut, B., Koksal, F. (2000). EPR spectra of VO2+ and Cu2+ ions in di-ammonium d-tartrate single Crystals, J. Phys. Chem. Solids 61, 1367-1372. [11] Abragam, A., Bleaney, B., Electron Paramagnetic Resonance of Transition Ions, Clarendon, Oxford, 1970. [12] Stevens, K.W. H. (1953). On the Magnetic Properties of Covalent XY_{6} Complexes Proc. Roy. Soc. A 219, 542-555. [13] Bansal, R. S. (1990). Electron Paramagnetic Resonance Studies of Doped Single Crystals, Ph. D. Thesis submitted to M.D University, Rohtak, India, p. 133. [14] Kripal, R., Singh, P. (2006). EPR and optical absorption studies on VO2+ ions in zinc lactate trihydrate J. Magn. Magn. Mat. 307, 308-312. [15] Kripal, R.,  Misra, M. G,  Lipinski, I. E. and  Rudowicz, C.  (2012). Electron paramagnetic resonance and optical study of   VO2+-doped zinc ammonium phosphate hexahydrate single crystals Phys. Scr. 86,  045602 (9pp). [16] Misra, B. N., Kripal, R. (1977).  Covalent Bonding Parameters of Complexes with Paramagnetic ions, Z. Phys. 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Crystalline Field Effect on bonding Parameters of VO2+ Ion

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Crystalline Field Effect on bonding Parameters of VO2+ Ion

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