ISSUE 182: OCTOBER-DECEMBER 2005

INSA Prize for Materials Science Award (2003) Lecture

Professor R Nagarajan, FNA, delievered the INSA Prize for Materials Science (2003) Award Lecture on November 22, 2005 at the School of Physics & Centre for Nonlinear Dynamics, Bharathidasan University, Tiruchirapalli. The title of his talk was “Discovery of Superconductivity in Quaternary Borocarbides”. Two hundred research scholars and M.Sc. Physics students from Bharathidasan University and in and around colleges from Tiruchirapalli attended his lecture. The lecture was well received and appreciated by the audience. To start with Prof. M Lakshmanan, FNA (Convener, Local Chapter) introduced Prof. Nagarajan to the audience. Prof. R Simon, FNA, Institute of Mathematical Sciences,
Chennai, who was present among the audience, read the citation. This was followed by the lecture of Prof. Nagarajan. Quaternary rare earth transition metal borocarbides are a new class of interesting superconducting and magnetic materials. Discovery of superconductivity at an elevated temperature (Tc »13K) in Y-Nni-B-C system–the first quaternary material to exhibit superconductivity–a decade ago at TIFR, Mumbai by Prof. Nagarajan and his collaborators led to these materials. Prof. Nagarajan, in his Materials Science Prize Lecture briefly outlined the background and the experiment on Yni4B that led to the discovery and gave an overview of the subject. The most surprising result namely the observation of signatures of superconductivity in the sample of Yni4B, as part of their investigations of properties of the Yni4B (R=Y, rare earth) series of compounds.The trace superconductivity (drop in resistance but not going to zero) was discovered with the superconducting transition temperature Tc »12K in the resistivity of Yni4B (C Mazumdar, R Nagarajan,L C Gupta, R Vijayaraghavan and B D Padalia, TIFR Annual Report 1991-92, p.77). This was an exciting discovery, as 12K is high ‘Tc’ for metallic systems (amongst thousands of superconducting materials only a few materials show Tc >10K, highest then known being 23K in thin film of Nb3Ge), prior to this very few Ni-based superconducting materials were known (even then with Tc >4.2K – the boiling point of liquid helium), certainly no ternary (compound or alloy containing three elements) and they published the findings (Chandan Mazumdar, R Nagarajan, C Godart, LC Gupta, M Latroche, SK Dhar, C Levy-Clement, BD Padalia, R Vijayaraghavan, Solid State Communications 87 (1993) 413). To find out the origin of the trace superconductivity, they synthesized and investigated a large number of Y-Ni-B alloys with different compositions. Amongst them superconductivity was found in three more compositions but only as a minority phase. All these experimental results pointed  towards the origin of superconductivity being likely to be due to the presence of material phase having an unintended fourth element. To verify this conjecture, they re-melted a sample of Yni2B with 0.2 atomic fraction of carbon © and investigated the properties. This sample exhibited zero resistance and also a dramatic enhancement in diamagnetic susceptibility below »13K confirming that carbon is an essential element in this new superconducting material. Remelting of alloys of other compositions which showed trance superconductivity with 0.2 atomic fraction of carbon, also produced zero resistance and enhancement diamagnetism. Heat capacity investigations showed maximum anomaly in the multiphase sample Yni2B3C0.2 indicating that maximum bulk nature of superconductivity occurs in this composition. Alloys of different compositions and element analysis showed that all the four elements are required for the new superconducting phase and that Y:Ni ratio is 1:2. Prior to this discovery, no four element intermetallic superconductor was known. Thus superconductivity in quaternary intermetallics was discovered (R. Nagarajan, C Mazumdar, Z Hossain, SK Dhar, KV Gopalakrishnan, LC Gupta, C Godart, BD Padalia and R Vijayaraghavan, Physical Review Letters. 72(1994) 274).Professor Nagarajan pointed out how his group’s work on superconductivity in intermetallic quaternaries laid foundation for the new subject – superconductivity and magnetism in quaternary rare earth transition metal borocarbides – most of them of RM2B2C – type (R=Y, Sc, U, Th, rare earth; M=Ni,Pd, Pt, Ir etc) of compounds.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 He also highlighted how the subsequent developments on superconductivity of quaternary borocarbides excited the scientific community with a possibility of new route to high Tc superconductivity (substituting Ni by Pd in the system produced a superconducting material with the then highest known Tc (23K) for intermetallics) and triggered intense work at many laboratories all over the world and revitalized research in intermetallic superconductors.He pointed out that high Tc of LuNi2B2C and Yni2B2C and availability of large single crystals in the clean limit has given opportunity to investigate some of the intricate aspects of the phenomenon of superconductivity which were not possible to investigate with earlier known superconductors. He also highlighted the fact that the some of the superconductors of this family have become model materials for detailed investigations of rare and exotic phenomenon of coexistence of superconductivity and magnetism. Professor Nagarajan concluded with the remarks that the manner in which the discovery was made and the subsequent developments represent a classic examples of process of science. He also pointed out that this discovery is perhaps one of the rare works in condensed matter physics from India to make an international impact, with the publication (R Nagarajan et al. Physical Review Letters 72(1994) 274) having citation index of more that 500.

International Activities

Indo-Russian Symposium on Organic Chemistry held at the Indian Institute of Science, Bangalore during November 7-8, 2005 The 1st Indo-Russian Symposium on Organic Chemistry (IISc, Bangalore, Nov7-8, 2005) had participation of the delegation of ten leading scientists from Russian Academy of Sciences including three full members of RAS (Academicians O.M. Nefedov, S.M. Aldoshin and V N Charushin), three corresponding members of RAS (M.P. Egorov, O.G. Siniashin, M.Y. Antipin) and four heads of laboratories (Professors N.E. Nifantiev, Y.V. Tomiliov, V.P. Ananikov and E.S. Finkelstein) respresenting six leading chemical research institutes of RAS. The perspectives of science and technology collaboration in the area of Organic Chemistry was discussed with the participation of the representatives of leading Indian research institutions (IISc, Bangalore; IICT, Hyderabad; University of Hyderabad; Central Salt & Marine Chemicals Research Institute, Bhavnagar; IIT, Madras, IIT, Mumbai; University of Madras; National Chemical Laboratory, Pune). The symposium was attended by over 100 young researchers drawn from different institutions in India.

The lectures delivered in the symposium encompassed many facets of organic chemistry including organometallic chemistry; new synthetic methodologies, carbohydrate chemistry, biologically active natural products, new chemical technologies and materials and chemical sensors. A round table discussion of all the invited speakers (from India and Russia) was held to identify a few important areas where there is commonality of interest for collaboration and cooperation in the future.Symposium laid emphasis on the Novel methodologies of organic synthesis; Catalysis in organic chemistry; Functional materials (sensors, devices etc.); Chemistry of natural compounds and bioactive molecules; Green chemistry; Chemistry of organofluoro compounds for future collaboration under INSA-RAS programme.The Russian scientist volunteered to organize the 2nd Indo-Russian Symposium on Organic Chemistry in Russia in the first half of 2007.


 


 


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