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1 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 1 Click Instructions for Viewers T heNMRS2004 T heNMRS2004 presentation is from slide # 2 onwards to # 15 At any instant during the viewing, the display can be advanced to the NEXT SLIDE/or the Next frame within the same slide by a simple mouse-click. After each mouse-click carefully watch for the change to the next display. Do not make too many Clicks at one instant. When you encounter a HYPERLINK (a green text box with faintblue font color with an underlining) a link-cursor(not an arrow) would appear on placing the cursor over the link and a mouse-click would display the linked slide. Then look for a return link to display again the source slide. Right-Click the mouse and exercise the FULL SCREEN viewing option even at the very beginning CLICK HERE for MR Symposia 2003 Presentation

2 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 2 NMRS 2004 Presentation Concerning the Specimen Sample-shape for the Single-Crystal HR PMR Studies S.Aravamudhan Department of Chemistry North Eastern Hill University Shillong (Meghalaya) INDIA 20th February 2004

3 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 3 A recapitualisation from the NMRS2003 presentation Slides 1-6 Bulk Susceptibility Effects In HR PMR Liquids D a = - 4 /3 D b = 2 /3 SOLIDS Single crystal arbitray shape Single Crystal Spherical Shape Induced Fields at the Molecular Site Lorentz Sphere cavity The conclusions earlier had been to find answer to the following questions: 1. Should the Lorentz Sphere be Spherical? For this a study of the convergence characteristics for summing over the lattice (cubic and noncubic) for ellipsoidal inner volume element (counter Lorentz sphere) This was the material at 3rd Alpine Conference Poster Once this question could be adequately answered, the next question was to find the consequences of inhomogeneities arising within the sample. Since even if the bulk susceptibility is the same through out the sample, the resulting induced field distributions will not be homogeneous within the samplefor shapes other than sphere and ellipsoid.

4 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 4 Size of the Cavity and the choice of its location in the Specimen can be varied to sample the induced field over the extent of the specimen Magnetic Field Demagnetization Effects i = i i /R 3 i [1-(3.RR i /R 5 i )] A link to a Web Site containing Features of Demagnetzation Factors Calculations A detailed exposition of this tensor equation Appears in the next slide #3

5 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 5 Isotropic Susceptibility Tensor = Induced field Calculations using these equations and the magnetic dipole model have been simple enough when the summation procedures were applied as described in the previous presentations and expositions. For example, an insight into the induced fields and demagnetization could be gained as depicted in the next slide which otherwise would have been hard to realize and prove so effctively.

6 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 6

7 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 7 These results could be dated back to the year

8 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 8 for a cubic parameter value of 9:9:9 the inner volume element was given an ellipsoidal shape with varying ellipsoidal shape parameters CZ BY and AX. In most of the cases BY= AX. In the plot referred to here CZ = 1.0 and BY was varied from1.0 to 0.8. This corresponds to the prolate case for the shape of ellipsoid as in the figure. as the shape becomes more ellipsoidal there seems a lot of deviation occurs in the radius range from 18 to 234 units. OR Some Results of the 3rd Alpine POSTER at France in Sept.2003 are summarized in the next three Slides 7-9

9 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 9 Compression of the scale on the Y-axis to 1 division= 1 x units from the value of 2 x units in the lower plot make the cubic case (spherical inner element) value to be all along the zero line !Monotonically increasing deviations from zero line (on the positive side) with increase in ellipticity!! The convergence value does not depend upon the ellipticity of the inner volume element. When the lattice is of cubic type A=B=C, then for all ellipticity including the limiting case of a sphere, the convergence of the lattice sum occurs to zero value. OR

10 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 10 Non-Cubic Cases: With a difference of 3 units in lattice parameters, for the two extreme cases of cubic lattices the summation leads to zero value all through for the various radius values. When the C= 10 and C=7 the convergence values range is far away from zero and the values are from -6 x to +4 x Lower trace the same cubic/noncubic values with ellipsoidal shape 1:0.7. Trends of variation in the x-axis regions of 100 units to 224 units indicate an increased deviation with ellipticity. As noted earlier for the cubic cases the convergence values are independent of the ellipticity even for non-cubic cases. Qualitatively, when the ellipticity ratio changes by 0.1, the convergence value changes at the rate of 4.5 x per 0.1 value change in the ratio. OR After the CUBIC Case...

11 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 11 TOP SHAPE CYLINDER Equatorial (0,7) (0,0) Results of Claculations made for this presentation at NMRS2004

12 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 12

13 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 13

14 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 14

15 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 15 END OF Presentation Questions & Comments To End this SHOW make a right-click and click further on the End Show option in the prop-up box.

16 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 16 Click Instructions for Viewers MR Symposia 2003 Presentation At any instant during the viewing, the display can be advanced to the NEXT SLIDE/or the Next frame within the same slide by a simple mouse-click. After each mouse-click carefully watch for the change to the next display. Do not make too many Clicks at one instant. When you encounter a HYPERLINK (a green text box with faintblue font color with an underlining) a link-cursor(not an arrow) would appear on placing the cursor over the link and a mouse-click would display the linked slide. Then look for a return link to display again the source slide. Test link HERE and RETURN to this first slide HERE Right-Click the mouse and exercise the FULL SCREEN viewing option even at the very beginning Click HERE for visiting the NMRS2003 Web Site

17 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 17 MR Symposia 2003 Presentation 5th February 2003 S.ARAVAMUDHAN Department of chemistry North Eastern Hill University, Shillong Can HR PMR Provide a Further Insight Concerning the Requirement of the Spherical Shape of Lorentz Cavity? Text of Abstract: CLICK here for hyperlink to slides 13 &14

18 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 18 Bulk Susceptibility Effects In HR PMR Liquids D a = - 4 /3 D b = 2 /3 SOLIDS Single crystal arbitray shape Single Crystal Spherical Shape Induced Fields at the Molecular Site Lorentz Sphere cavity

19 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 19 Size of the Cavity and the choice of its location in the Specimen can be varied to sample the induced field over the extent of the specimen Magnetic Field Demagnetization Effects i = i i /R 3 i [1-(3.RR i /R 5 i )] A link to a Web Site containing Features of Demagnetzation Factors Calculations LINK to Graph Click Here Click Here for the consideration of Variety of possibilities for the lattices and site symmetries

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21 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 21

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23 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 23 The Simpler method (Details to be viewed optionally from other slides)of calculating Demagnetizing fields makes it possible to consider different combinations of Macroscopic sample Shape with appropriate hypothetical Cavity shapes to increase the utility of HR PMR measurements in Solids Various Specimen shapes with the variety of Cavity shapes It may be necessary to calculate the intermolecular contributions inside the Spherical samples with an elliptical shape of the lorentz sphere and find the conveniences of calculating. (Link for details / CLICK option)CLICK option If it is possible to obtain some well defined shape(not necessarily Spherical) specimen of the single crystal samples on which HR PMR studies have well established results, then the experiments can be made with such shapes by orienting them in 3 independnt rotation axes and try to simulate that shape with the same ratios of the sides and faces but at the range of the Lorentz sphere (about 100 A° ) and calculate the intermolecular lorentz type contributions with the Demagnetizing field type calculation and retrieve the intra molecular contribution as it was done with the spherical samples and reproduce those values. CLICK HERE CLICK HERE For a glimpse of Crystal systems as well

24 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 24 END OF Presentation Questions & Comments To End this SHOW make a right-click and click further on the End Show option in the prop-up box.

25 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 25 Return display to slide 4

26 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 26 Return display to slide 7 Click to reach for the Web Site LINKS

27 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 27 Link to Internet Web Sites Link #1 for details of Calculations of Induced Fields and Demagnetization Factors Link #2 Link #3 Link #4

28 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 28 Abstract for the MR Symposia 2003, IISc., Bangalore, Feb. 2-6,2003 CAN HR-PMR PROVIDE A FURTHER INSIGHT CONCERNING THE SPHERICAL SHAPE OF LORENTZ CAVITY? S.Aravamudhan Department of Chemistry North Eastern Hill University Shillong Meghalaya India a The Lorentz Cavity, a hypothetical void carved out inside a material medium while considering the demagnetizing fields at a point (site) inside the material- specimen, is conveniently described to have a spherical shape since the demagnetization factor value for spherical external shape is obtained by the spherical symmetry requirement for such shapes in the homogeneously magnetized materials. For the case when the external shape is spherical and if, the carved out cavity also is spherically shaped, then for the inside void one can have the same numerical value, but negative in sign, as for the spherical outer shape which encompasses a spherically filled material specimen. This can result in the required zero Induced fields at the sites inside the material medium.Then for an ellipsoidal outer shape, it would be possible to get induced field values by using the demagnetization factor values for ellipsoidal outer shape and the already eastablished value for the hypothetically carved out spherical lorentz cavity. Click for continuation Abstract in the next slide Web Site:

29 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 29 In the previous reports (1) on Calculation of Induced Fields by Simple Summing Procedures and thus, the calculation of Demagnetization Factors, it is mentioned that the requirement of zero induced field in case of the spherical outer shape for the specimen has been calculated by this procedure as well. It is being contended here that the Calculated Induced Field inside a Ellipsoidally shaped specimen can be equal to zero if the carved out cavity inside the specimen also has the same ellipsoidal shape since the demagnetization factor for the inner cavity shape and the outer Specimen shape should be equal in magnitude and opposite sign. HR PMR in solids, as it would be explained in the presentation, seem to provide a unique context to acquire a better insight into the necessity for a spherically shaped specimens for obtaining only the intramolecular symmetry determined shielding tensors. An inquiry as to what the shape of the Lorentz cavity can also be becomes possible by being sensitive enough for the intermolecular contributions to Shielding tensors from the neighbouring molecules and groups around a given particular proton site which can be calculated by the recently reported simple procedure(for even the hitherto unreported shapes) and, by considering these aspects by the experimental determination of the proton shielding tensors in single crystals and supplemented with the necessary calculated (anisotropic) induced fields at the site which should take the considerations of shape dependences of such fields appropriately. Ref: (1) Web Site: and the HOTLINKS at and from CLICK HERE CLICK HERE to return display to sd #2

30 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 30 Spin Precession Animation DEMO Precession Starts Automatically ReturnReturn to(#1) first slide Nuclear Spin

31 7/23/ :59:19 AMNMRS 2004 : S.Aravamudhan: 20th feb 2004: 31 Crystal Systems CLICKCLICK to Return to slide#4 CLICKCLICK to Return to slide#8

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