Seminar By Yaroslav Mudryk, Iowa State University
Title: Temperature and Magnetic Field Induced Structural Transformations in Rare Earth Intermetallics
Host: Theo Siegrist
Abstract: A growing number of modern and futuristic functionalities discovered in solid state materials can be linked to a variety of phase transformations exhibited by these materials in response to a change in external stimuli. In particular, discovery of novel magnetostructural transformations — simultaneous changes of both crystallographic and magnetic sublattices — enabled magnetic refrigeration to become a viable alternative to conventional vapor-compressor technology for cooling and heat-pumping applications over extended range of temperatures. Other technologically attractive phenomena, such as giant magnetostriction and magnetoresistance, and kinetically arrested magnetic states are often observed during these transformations due to intimate coupling of magnetism and crystallography. At the same time, further advances in our fundamental understanding of these transitions are needed to increase both ability and availability of magnetic functional materials.
Rare earth intermetallic compounds are especially exciting systems to study temperature and magnetic field induced structural transformations due to great variety of available compositions, transition types, and mechanisms. Of particular interest are rare earths compounds without d-elements presenting unconventional mechanisms of strong magnetic exchange and magnetostructural coupling. Our systematic investigation of such systems using temperature- and magnetic-field dependent x-ray powder diffraction complemented by magnetic and heat capacity measurements as well as density functional theory calculations has led to several interesting and important discoveries that are shaping both basic and applied science of rare earth compounds and opening new venues in the search for novel functionalities. At first, we will discuss the R5T4 systems, where R is rare earths and T is 13-15 group element that are well-studied model examples of magnetoresponsive rare earths compounds; than recent results on other R-T based systems will be presented, highlighting the enormous potential of such systems for new energy related science.
The Ames Laboratory is operated for the U. S. Department of Energy by Iowa State University of Science and Technology under contract No. DE-AC02-07CH11358. This work was supported by the Department of Energy, Office of Basic Energy Sciences, Materials Sciences Division.