Conference: Metastabilities across first-order transitions in magnetic functional materials

Vasudeva Siruguri UGC-DAE Consortium for Scientific Research Mumbai Centre, R-5 Shed, BARC Campus, Mumbai – 400 085, INDIA

Vasudeva Siruguri, member of the UGC-DAE Consortium for Scientific Research Mumbai Centre, will discuss the phenomenon of Kinetic Arrest (KA) in a variety of magnetic functional materials like CMR manganites, magnetic shape memory alloys, magnetocalorics, multiferroics, which exhibit first order phase transitions. It has been observed that the kinetics of the phase transformation can be influenced critically by an external magnetic field and can be arrested when cooled under an appropriate external magnetic field, thereby inhibiting the transformation to the low temperature equilibrium phase. Thus, a KA state could have magnetically ordered coexisting metastable and equilibrium (transformed) phases and has been termed as a magnetic glass. The phase coexistence is established by using a novel measurement protocol called CHUF (Cooling and Heating in Unequal Fields). They have used neutron diffraction along with the CHUF protocol, for the first time, to show the phenomenon of kinetic arrest in several magnetic functional materials. The devitrification of the arrested phases into their low temperature equilibrium phases at the characteristic temperature TK(H) and their subsequent reentrant transition to the high temperature equilibrium phases, unambiguously demonstrates the glassy nature of the arrested states. Some analogies are drawn between the dynamics involved in such a glass and that observed for structural glasses.

  The Mumbai Centre of the Consortium for Scientific Research (CSR) promote Neutron Beam Research among university groups in India. The major research activities of the CSR, Mumbai Centre, are in the following two fields:

• Soft Condensed Matter: Surfactants, Polymers, Block-co-polymers, Gels.
• Magnetism: Perovskite oxide materials, GMR, CMR, Intermetallics.