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Manipulating Polar Ferromagnetism In Transition Metal Doped Zno: Why Manganese Is Different From Cobalt, Kevin R. Kittilstved, D. R. Gamelin
Manipulating Polar Ferromagnetism In Transition Metal Doped Zno: Why Manganese Is Different From Cobalt, Kevin R. Kittilstved, D. R. Gamelin
Kevin R. Kittilstved
High-temperature magnetic ordering in Mn2+- and Co2+-doped ZnO diluted magnetic semiconductors has been predicted theoretically and confirmed experimentally to have different charge-carrier requirements. This paper summarizes some of these experimental and theoretical results and relates the different carrier polarity requirements for 300 K ferromagnetism in Mn2+:ZnO and Co2+:ZnO to differences in the charge-transfer electronic structures of these two materials.
Magnetic Circular Dichroism Of Ferromagnetic Co2+-Doped Zno, Kevin R. Kittilstved, J. Zhao, W. K. Liu, J. D. Bryan, D. A. Schwartz, D. R. Gamelin
Magnetic Circular Dichroism Of Ferromagnetic Co2+-Doped Zno, Kevin R. Kittilstved, J. Zhao, W. K. Liu, J. D. Bryan, D. A. Schwartz, D. R. Gamelin
Kevin R. Kittilstved
Cobalt-doped ZnO (Co2+:ZnO) films were studied by magnetic circular dichroism (MCD) spectroscopy. A broad 300 K ferromagnetic MCD signal was observed between 1.4 and 4.0 eV after exposure of paramagnetic Co2+:ZnO films to zinc metal vapor, attributed to low-energy photoionization transitions originating from a spin-split donor impurity band in ferromagnetic n-type Co2+:ZnO.
Direct Kinetic Correlation Of Carriers And Ferromagnetism In Co2+:Zno, Kevin R. Kittilstved, D. A. Schwartz, A. C. Tuan, S. M. Heald, S. A. Chambers, D. R. Gamelin
Direct Kinetic Correlation Of Carriers And Ferromagnetism In Co2+:Zno, Kevin R. Kittilstved, D. A. Schwartz, A. C. Tuan, S. M. Heald, S. A. Chambers, D. R. Gamelin
Kevin R. Kittilstved
The hypothesis that high-Curie-temperature ferromagnetism in cobalt-doped ZnO (Co2+: ZnO) is mediated by charge carriers was tested by controlled introduction and removal of the shallow donor interstitial zinc. Using oriented epitaxial Co2+: ZnO films grown by chemical vapor deposition, kinetics measurements demonstrate a direct correlation between the oxidative quenching of ferromagnetism and the diffusion and oxidation of interstitial zinc. These results demonstrate controlled systematic variation of a key parameter involved in the ferromagnetism of Co2+: ZnO and, in the process, unambiguously reveal this ferromagnetism to be dependent upon charge carriers. The distinction between defect-bound and free carriers in Co2+: ZnO …