Howard A. Blackstead

Professor,
Condensed Matter Physics

Research Interests
The objective of the program directed by Prof. Blackstead is to discover new high temperature superconductors and to develop electronic device applications using these materials. Currently, we are studying materials in the class A₂LnRu_1-uSr₂Cu_uO₆ where A is an alkaline earth, Sr or Ba, and Ln is a lanthanide or Y. These materials are very attractive, since they are doped with a metal ion, not oxygen, and have (near) cubic symmetry. The superconducting transition temperatures are as high as 89K. We are growing crystals of these materials using a recently acquired traveling solvent floating zone (TSFZ) system, and we are experimenting with different doping strategies. Our measurement capability includes: resistivity, magnetization, and microwave frequency (5-80 GHz) surface resistance, as functions of temperature and applied magnetic (0-7T) field. Additionally, we have a femto-second laser system for the study of carrier dynamics. With collaborators, we carry out additional studies including: muon spin rotation, neutron diffraction, Mössbauer, and specific heat measurements.

Selected Publications:

“Magnetically ordered Cu and Ru in Ba₂GdRu_1-uCu_uO₆ and in Sr₂YRu_1-uCu_uO₆,” H.A. Blackstead, J.D. Dow, D.R. Harshman, et al ., Phys. Rev. B 63 (21) , 214412 1 (2001).

“Magnetic susceptibility and resonance studies of ordering in Ba₂GdRu_1-uCu_uO₆ ,” H.A. Blackstead, J.D. Dow, D.R. Harshman, et al ., Solid State Comm. 118 (7) , 355-359 (2001).

“Magnetism and Superconductivity in Sr₂YRu_1-uCu_uO₆ and in Ba₂GdRu_1-uCu_uO₆ ,” H.A. Blackstead, J.D. Dow, D.R. Harshman, M.J. DeMarco, M.K. Wu, D.Y. Chen, F.Z. Chien, D.B. Pulling, W. J. Kossler, A.J. Greer, C.E. Stronach, E. Koster, B. Hitti, M. Haka, and S. Tooronigan, Eur. Phys. Journal B . 15 , 649-56 (2000).

“Location of the Superconducting Hole Condensate in Sr₂YRu_1-uCu_uO₆ by m⁺ SR,” D.R. Harshman, W.J. Kossler, A.J. Greer, C.E. Stronach, E. Koster, B. Hitti, M.K. Wu, D.Y. Chen, F.Z. Chien, H.A. Blackstead, and J.D. Dow, Physica B 289-290, 360 (2000).

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