Antiferromagnetic d-electron exchange via a spin-singlet pi-electron ground state in an organic conductor.
Electron spin resonance reveals the spin behavior of conduction (pi) and localized (d) electrons in beta-(BDA-TTP)2MCl4 (M=Fe, Ga). Both the Ga3+(S=0) and Fe3+(S=5/2) compounds exhibit a metal-insulator transition at 113 K with the simultaneous formation of a spin-singlet ground state in the pi electron system of the donor molecules. The behavior is consistent with charge ordering in beta-(BDA-TTP)2MCl4 at the metal-insulator transition. At 5 K, the Fe3+ compound orders antiferromagnetically, even though the pi electrons, which normally would facilitate magnetic exchange, are localized nonmagnetic singlets.
National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA.
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T
Tokumoto
J S
JS
Brooks
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Y
Oshima
E S
ES
Choi
L C
LC
Brunel
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H
Akutsu
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Kaihatsu
J
J
Yamada
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J
van Tol