INTRODUCTION:

The reports are found to have to have synthesized Fe/Cr/Fe trilayers and Fe/Cr multilayer. The trilayers have found to possess antiferromagnetic properties¹ and the multilayers have found to have giant magneto-resistance (GMR)². They show superconducting, elastic and optical properties also.³ Themultilayers (tri or poly) are simply the interlocking of non-magnetic or anti-ferromagnetic layer like Fe-Co-Ni. But still very less work has been reported.

Clusters are considered as intermediates of molecules and surfaces in the progressive hierarchy of atoms, molecules, surfaces and solids. They are the stable aggregates of atoms or molecules held together under various conditions. They can be supposed as the artificial molecules. They are metastable and can grow by interaction with atoms or clusters.

The gas phase reactivity of Fe, Co and Ni transition metal elements (TME) of iron family metal clusters with H₂, D₂, CO and NH₃ has been found to show large size dependent fluctuations.^4,5,6The change in electronic structures and the atomic sites available on the clusters effects the change in reactivity of the clysters twice of thrice.

The values of ionization potential and catalytic/optical properties of the clusters with respect to the size makes merry of bulk magnetic and metallic properties.^7-10For most magnetic materials, the critical size is in the range of 20-2000 nm. Reports are found for the noble metal particles in sol from^11-14 but probably because of higher reactivity of TME of iron family (Fe, Co, Ni) very few references are found.

Herein we target, hence, the synthesis of multilayers and clusters of these iron family TME.

EXPERIMENTAL:

SYNTHESIS OF MULTILAYERS:

The Nickel-copper multilayers are framed for many (m+n) supercells. They theoretically have body centred tetragonal structure. Starting from (3+3) super cell, the no. of Nickel and Coppers layers are to be progressively increased to from (7+5), (5+7), (9+7), (7+9), (11+9), (9+11) super cells and the layering at which structural relaxation occurs is to be experimented. It is also to observe and calculate that whether the atomic spheres overlaps are well within the permissible limits. With increase in multilayer thickness, the magnetic moments are to be recorded. The Nickel layer at the interface achieves required charge due to interfacial Copper and neighbouring nickel to exhibit magnetic moment. Most probably with increase in Nickel layers, the magnetic moment may not be exhibited to that extent and even may not show any magnetic moment¹¹because Cu-layers also show a slight polarization.

Similarly Fe-Cr, Fe-Sn, Cr-Sn multilayers are also to be studied.

SYNTHESIS OF MAGNETIC CLUSTERS OF Fe, Co and Ni-TME:

It is known fact that the metal ions on reduction in aqueous solutions gives metallic clusters which ultimately form metallic particles. The stabilize these particles in sol form, poly vinyl alcohol, polyphosphate and poly-acrylic acid is used. The surface plasmons so formed can be confirmed by uv-visabsorption spectrum.

The required sol for FeSO₄, CoSO₄ and CrSO₄ are to be synthesized by the procedure below.

The nano pure water, the salts, sodium formate and gelatin (most chemicals from Merck or BDH) are to be used. The gelatin gets swollen when soaked in water for 10-15 min, then warmed for 2-3 min at 313K-323 K in a water both with continuous stirring. All solutions to be used will be freshly prepared, deareated by bubbling with high purity N₂. Phosphate buffer will be used to study the reaction at pH7.

The metal sol is to be produced by -radio irradiation of the solution of 1.0x10^-3 mol dm³salt, gelatin (0.1%W/V) and 5x10^-3mol dm³, formate (pH7). The solution is protected from light to avoid any photochemical reactions.

The sol is finally heated at around 373 K for 2 hours and then centrifuged, to get the nano-sized metal particles.

CONCLUSION:

The prompted literature survey leading to afore said synthesis of the multilayers and the clusters of the TME-iron family elements along with other elements may be fruit full in getting the antiferromagnetic and limited range magnetic nanometal particles.

ACKOWLEDGEMENT:

The authors are thankful to the library of IICT-Hyderabad, and the library of NISCAIR for providing literature.

REFERENCES:

1. Gruenberg P, Skhreiber R, Pand Y, Brodsky M.B. and Sowers H, Phy Rev. Lett. 57 (1986) 2442.

2. Baibich M. N., Broto J. M. et al, Phy Rev. Lett 61, (1988) 2472

3. Jin B. Y. and Keterson J. B. AdvPhy38 (1989) 1989

4. Richtmeister S. J. et al, J ChemPhy 82(1985) 3569

5. WeilleterBH et al, J ChemPhy91 (1986) 4714

6. Rilley S J et al, Clusters of Atomic and Molecules, 11, 56 (1994) 221

7. Relley S J et al, Gas phase chemicals Reactions of Transition Metal Clusters with simple molecules : Jena P, Rao BK and Khanna SN, 277 (Plenum, New York) 1987.

8. Parks E K, Nieman G. C. et al, J ChemPhy (1987) 1066

9. Kaldor A et al, AdvChemPhy70 (1988) 211

10. Marignier J L et al J chemPhy85 (1988) 21

11. Jarlborg T et al Phys Rev Lett, 45 (1980) 653.

Received on 09.01.2014 Modified on 14.02.2014

Asian J. Research Chem. 7(3): March 2014; Page 321-322