Have resonance experiments seen macroscopic quantum coherence in magnetic particles? The case from power absorption

Recent magnetic resonance experiments on ferritin and nanofabricated magnetic dots of Fe(CO${)}_5$ have been interpreted in the framework of macroscopic quantum coherence (MQC). The power absorption in MQC is calculated and shown to be exceeded by a factor of 50 to 150 in the ferritin experiments. Alternative microscopic causes for the resonance are suggested. In the Fe(CO${)}_5$ experiments, MQC predicts no resonance at all at the ac fields involved, and the power absorbed is ${10}^{18}$ times larger than expected.