Bagchi, R N

Pal, A K

Saha, P R

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E.P.R. INVESTIGATION ON ORTHORHOMBIC g-TENSORS IN COPPER RUBIDIUM SULPHATE HEXAHYDRATE, COPPER CESIUM SULPHATE HEXAHYDRATE AND COPPER THALLIUM SULPHATE HEXAHYDRATEA. K. PAL, R. N. BAGCHI, P. R. SAHA AND R. K. SHAHAMagnetism DepartmentIndian Association for the Cultivation of Science,J adavpuk, Caloutta-32. I ndia(Received May 30, 1967)ABSTRACT. Electron paramagnetic resonance technique has been employed to deter- mine precisely the orthorhombic (/-tensors and their orientations in the imit coll in three copper tutton salts, namely, copper rubidium sulphate hexahydrate, copper cesium sulphate hoxahy- drate and copper thallium sulphate hexaliydrate. The results have been compared with those of other Tutton salts reported earlier (Bose et al, 1964 ; Ghosh eL al., 1965). Tho comparison brings out clearly appreciable variation in the nature of the ligand field from salt to salt, pre­sumably due to the long range effect arising from distant neighbours outside the primary ligand cluster.I N T R O D U C T I O NIn previous communications (Bose et oZ, 1964; Ghosh et al, 1965) it has been shown that the e.p.r. method can be conveniently utilized in probing the three orthorhombic axes of the magnetic complex and finding the three principal ionic gr-values in the single crystals of copper tutton salts. The results of application of the method to tho case of copper potassium sulphate hexahydrate, copper ammonium sulphate hexahydrate, copper potassium selenate hexahydrate and copper ammonium selenate hexahydrate have been reported in that connection. The same method has been adopted to three other tutton salts, copper rubidium sulphate hexahydrate, copper cesium sulphate hexahydrate and copper thal­lium sulphate hexahydrate; and the results are discussed in the present paper.M E T H O D  OP  M E A 8 U B B M E H TIn all these salts variation of values was studied at room temperature in four natural planes of the crystals, namely c(001) plane, 5(010) plane, {(Oil or OH) plane and p(110 or llO) plane with the help of 1.2om transmission type e.p.r. spectrometer (Ghosh et al, 1963). Actually measurements in three planes are sufficient for determining the Ots' denoting the principal ionic g-values and their orientations, but the measurement in an additional plane has been used to make a check on the final results.101856. K a -  t h , M a  i„e,u?v z s : t : r r . :ob taim ^ . t  c o m y ,„ d .„ g ly  ,lifTe™ ,.  given i t a .  n t m terval. o t 10’ («m otlm e. 5«) and the g ..„ ,„ e . have b«,n p le tWaganm t the a n ^ a r  m o tio n ,. The g .„ .a l  cgnation of the g ..ellip» id  a , .h o»n  earlier (Bose e t at, 1964) is » r  * «wu^u-^*+C28l^‘‘+?s8^2+2Ci*X7+%,F2:4-2CijJZ =  i,whereM.PM. Investigation on Orthorhombic g-Tensora 867= S c.i^l8V-32 f;t33 -- £i«lin which a,-, /?,, yj represent the direction cosines of (?, relative to the orthogonal X(«), 7(6) and Z(c') axes of the crystal respectively.R E S U L T S  A N D  J) I S C  U S S I O NProm the above measurements the six independent coefficients i^jS defining the g^ -^ellipsoid have been determined. These arc given in table 1.Table 1Cll 2^3 i*33 1^13 C2 3Cu(RbSO.)a.6HaO 5.217 4.995 4.210 0.600 0 -0 .125C,i(CRSOg),.6HaO 5 215 5.010 4.487 0.655 0.209 -0.029Ou(T180g)a.6HjO 5.211 5.002 4.407 0.682 0.234 -0 .193By the method of matrix diagonalisation, from these six coefficients in each of these salts the principal (/-values and their orientations have been obtained. The principal gr-values and their orientations are shown in tabic 2 and table 3 respectively. The exj>eriraental data for other tiitton salts reported elsewhere (Bose et al, 1964; Ghosh et al, 1965) are also included in tables 2 and 3 for comparison.I t  will be seen from table 2 that the gf^ -ellipsoids in all these salts arc of definitely orthorhombic symmetry. It will be seen by examining table 3 that the angle, the 6?g-axis makes with the symmetry axis of the monoclinic crystal (i*e.6-axis) is nearly the same for all the salts. On the other hand, all other angles vary appreciably for the different salts. This is perhaps due to the fact that in all the salts 0^ axis coincides with the approximate tetragonal axis of the para­magnetic complex and the difference in orientations in the different salts arise from a distribution of alkali atoms or acid radicals, which vary from salt to salt, 9868 Palf Bagchi, Saha and ShahaTable 2Gi Ga ffaCu(KSO«)a. 6HaO* 2.055 2.167 2.384Cu(NH.SO.)a.6HaO* 2.063 2 .20e 2.35bCu(Rb SO^la.eHaO 2.04a 2.127 2.39aCu(Cs SO«)a.6HaO 2 .0?5 2.149 2,407Cu(Tl SO*)a.6HaO 2.027 2.17o 2.40eCu(KSoO«)a.6HaOt 2.07s 2 . I 64 2.367Cu(NH4SeOJa-6HaOt 2.063 2 . 12a 2.39a*Bose Bt al, 1964, fGhosh et al, 1965.Table 3Cofl'"^ ai Cos^ f^ii Co8“ y^i Cos'^a2 Co8~^ /?2 Cos~^Y2 Cos^ a^a Cos'^ P^a Cos'^ YgCu(KS04)2.6Ha0 72^8 10G^9 24°. 6 64°. J 134°.1 114°.4 41M 49° 92'^  (48°.6)*Chi(NH4S04)a.6Ha0 109°.9 116°.7 33°. 5 41°.9 131°.8 92°. 2 f)4“.9 52°.7 56°. 6 (49°. 6)*Cu(KSe04)a.6Ha0 108°.9 104°. 5 23°. G 49° 139° 89°. 4 4C“.5 52°. 6 66°. 5 (50°. 7)*Ou(NH4Se04)a.6HaO 92°. 2 128° 38°. 1 3G\6 119°.3 109°.9 53°. 6 61°.9 69°(5 r.)*Cu(RbS04)a.6Ha0 98°.5 76°.1 17°.3 r> r .2 13G°.3 73° 40M 60°. 1 93°. 1 (49°.8)^Cu(C8S04)2.6Ha0 121°.5 59°.4 46°. 8 67°. 5 125°.3 43°. 8 40*. 3 60°.3 83°.8 (50°. 9)*Cu(TlS04)a.6HaO 118°.2 58°.9 44°. 6 63°. 9 124°. 3 45°. 6 40*. 2 49°.9 87°.8 (49°.7,*♦ Angular values within parentheses are the angles obtained from magnetic anisotropy oxporimonts (Bose et al, 1957) on tho assumption of approximate tetragonal symmetry about the (7a 3^cis.packed about the equatorial plane of the complex without affecting appreciably the relative orientations of the symmetry axis. The orientation angles do not appear to bear any strict sequence to the ionic radii of the alkali atoms or tho acid radicals. It appears that the NH, and T1 sulphate salts which do not strictly belong to those of the alkali metal series K, Rb and Os, have decidedly a more pronounced orthorhombioity of the ligand field. Their angular orientations except008-1 also do not fit in the sequence of the other three sulphate salts. In the solenate salts, however, this larger orthorhombicity appears to bo largely compen­sated by the presence of SeOi~* ion.Variation in the gr-tensor in the isomorphous Tutton salts indicates very clearly tha t the ligand field, especially its anisotropic part., is not only dependent on the primary ligand cluster but also upon what are the more distant neighbours and how they are situated, in short what Is their effect upon the Cu*+ ion directly or indirectly through the immediately neighbouring water dipoles, since in the isomorphous series of salts it is only some of these distant neighbours which are different. The information, however, ii as yet far from complete and situation is too complex to render an accurate explanation of the said difference in aniso­tropy behaviour.A C K N O W L E D G M E N TThe authors are indebted to Prof. A. Bose, D.Sc., F.N.I. for valuable sug­gestions and advice.E.P.R Investigation on Orthorhombic g-Tensors 859R E F E R E N C E SBose, A., Ghosh, XT. S., Bagolii, R. N. and Pal. A. K., 1964, Indian J. Phys., 88, 381. Boso, A., Mitm S. C. and Sunil K. DuUa, 1957, Proc, Roy. Soc., A2S9, 105. Ghosh, U. S., Bag(W, R, N. and Pal, A, K „ 1903, Indian J. Phys. 87, 555.Ghosh, U. S., Pal, A. K. and Bugchi, R. N., 1905, J. Phys. Chem. Solids, 26. 2041.

E.P.R. Investigation on Orthorhombic g-Tensors in Copper Rubidium Sulphate Hexahydrate, Copper Cesium Sulphate Hexahydrate and Copper Thallium Sulphate Hexahydrate

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E.P.R. Investigation on Orthorhombic g-Tensors in Copper Rubidium Sulphate Hexahydrate, Copper Cesium Sulphate Hexahydrate and Copper Thallium Sulphate Hexahydrate

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