Condensed Matter Seminar

C³O:  Complex Complexity in Complex Oxides

Professor Lance DeLong
University of Kentucky, Lexington

Friday, November 6, 2009 - 4:00 P.M., NSH 127

3d-transition metal oxide materials have been intensively studied for applications in emerging technologies, including colossal magnetoresistance (CMR) manganites used in data storage devices, high-TC cuprates used in superconducting levitation devices, and a number of prospective materials (e.g., Fe₃O₄ and CrO₂) under study for next-generation spintronics applications.
 
4d- and 5d-transition metal oxides are less studied, but they exhibit a rich spectrum of exotic phenomena:  Recent discoveries* at the University of Kentucky include high-temperature ferromagnetism within a semiconducting state, a novel topological Hall effect, CMR in a bulk single crystal, and a very strong magnetoelectric effect due to a spin-orbit-induced metal-insulator transition.  The complex behavior of these materials is due to a strong competition between bonding, magnetic exchange, crystalline electric field, spin-orbit and magneto-elastic interactions, which is not found among the lighter 3d-transition-metal oxides and heavier 4f-rare-earth materials.

Emphasis will be placed upon the R-Type Ferrites, (Sr,Ca)(Fe,Co,Mn,Ti)_2+xRu_4-xO₁₁, that exhibit magnetic order at temperatures as high as 488 K and concomitant narrow-gap semiconductivity and magnetotransport properties that are promising for spintronic applications.  The R-Type Ferrites also present unique examples of fundamentally interesting and novel phenomena such as magnetic frustration on a disordered Kagomé lattice, spin chirality and a topological Hall effect.

* Work done by and with Prof. Gang Cao and Dr. Larysa Shlyk under the support of U.S. DoE Grant No. DE-FG02-97ER45653 and NSF Grant Nos. DMR-0552267 and EPS-0814194.

 

Please note different day and location.

 

Host: Boldizsar Janko