A minimal model, consisting of a 4 × 4 Hamiltonian and pertaining to a single Mn-O-Mn bond in the manganites, is introduced and solved to elucidate the physics of the dynamical Jahn-Teller effect on the double-exchange (DEX) interaction. The effect originates from the coupling of the motion of the bridging oxygen atom to the Mn electrons. It is shown that (i) the DEX interaction is considerably reduced by the dynamical Jahn-Teller effect and (ii) this reduction depends on the oxygen mass leading to an isotope shift in the Curie temperature, T c ∝ M α , with α ∼ 0.2. The isotope shift is found to depend sharply on the electron hopping parameter t. The exact results are also compared to the results obtained from both the adiabatic and the diabatic approximations.

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An excellent 64Mb chainFeRAM TM using a highly reliable capacitor with damage-robust MOCVD-PZT and SrRuO 3 /IrO 2 top electrode (TE) is successfully demonstrated for the first time. A very large signal margin of 540mV at 1.8V is achieved for the capacitor as small as 0.19µm 2 . Large sensing margin is well maintained after 85°C storage, and 10 years lifetime is successfully guaranteed. The combination of damage-robust MOCVD-PZT and optimized SrRuO 3 /IrO 2 TE as well as a sophisticated 'chain' structure that has a small bit line capacitance (Cb) nature shows excellent reliability and scalability. This work demonstrates that high density 256Mb chain FeRAM with 0.1µm 2 planar capacitor can be realized.

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