hppd-mukherjee

					Title: Proposal for high pressure, low temperature and high magnetic field investigations
in condensed matter
Proposer: G.D. Mukherjee, High Pressure Physics Division, Bhabha Atomic Research
           Centre

         The discovery and refinement of new materials and characterization tools, extension of
the accessible phase space (pressure, magnetic field and temperature), development of major
facilities (synchrotron & neutron sources) and an interdisciplinary approach are the major factors
that have yielded spectacular progress in condensed matter recently. Both hypothesis-driven and
curiosity-driven basic research has opened up unexpected phenomena and applications. While
researcher driven instrumentation is still relevant, access to large facilities via peer reviewed
proposals and access to large number of routine characterization tools maintained by separate
support groups are emerging as essential components of modern experimental investigations.
Here we propose the setting up of a high magnetic field facility, which will be useful for many
groups and can also be, coupled to the current the facilities in HPPD. Possible investigations that
are relevant to DAE programs and also to basic science that can be carried out are indicated.
         The refinement of the properties of the novel materials for employing them for various
practical applications demands a thorough understanding of the basic physics, which can only be
done with a proper delineation of the nature of their ground state in which different competing
interactions are active. This is best done by disturbing the ground state by changing the
temperature, pressure or magnetic field. Material behaviour under combined low temperature-
high pressure and intense magnetic field is an emerging field that is yielding spectacular
phenomena. As an example, a quasi one dimensional organic material, (TMTSF)2PF6 under
various temperature- pressure – magnetic field can exist as a metal, semimetal, semiconductor,
insulator, antiferromagnet, and superconductor (even at 6 tesla).
         Just like high pressure, high magnetic field also tunes material properties without
introducing chemical disorder, which in turn induce variety of new phenomena in materials.
Application of intense magnetic field can change the electron distribution of a solid and also
quantifies its electronic and spin states. In addition, for dc fields, the external magnetic field
penetrates all materials (except type I superconductors), which allows for resonance experiments
like EPR, NMR etc for obtaining important and new information on the local structure. Therefore
increasing the magnetic field strength will widen the field of resonant conditions, thus increasing
the resolution of structural information on any material. In view of the above the high magnetic
field along with low temperature and high pressure has become important for studying materials
with strong electron correlation.
         In HPPD, we are involved in the synthesis of new phases and investigation of the phase
stability of materials under high pressure and high temperature by variety of techniques; angle
dispersive X-ray powder diffraction, AC and DC conductivity, dielectric constant, Raman,
Mossabaur measurements. We are in the process of extending the measurements to low
temperature –high pressure.
         In view of the above, we propose building of a high magnetic field facility in BARC on the
lines of National High Magnetic Field Facility, Tallahassee, USA. Our interest as a user group is
to subject suitably chosen complex and novel materials to the extreme conditions of pressure,
temperature and magnetic field. This will reveal / characterize the unique properties in them.
Keeping the above view in mind, we propose studies on the following class of materials.
A) Strongly correlated electron systems (transition metals, Lanthanides, actinides and their
      compounds) due to their complex and rich electronic and magnetic properties.
B) Organic & strongly correlated electron superconductors.
C) Synthesis & characterization of higher specific strength materials with tailored thermal
      expansion coefficient, thermal conductivity etc.
   It may also be noted that investigations under high magnetic field will yield relevant information
in chemistry and biology as well, and the user community can be very broad.

				
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posted:5/12/2011
language:English
pages:1