Pressure-induced coordination crossover in magnetite, a high pressure Mossbauer study
Pressure-induced coordination crossover in magnetite, a high pressure Mossbauer study
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DOI：
10.1016/j.jpcs.2003.12.013
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发表时间：
2004-08
影响因子：
4
通讯作者：
M. Pasternak;W. Xu;G. Rozenberg;R. Taylor;R. Jeanloz
中科院分区：
文献类型：
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作者：
M. Pasternak;W. Xu;G. Rozenberg;R. Taylor;R. Jeanloz
温度依赖的57 Fe穆斯堡尔谱到40 GPa表明，Fe 3 O 4磁铁矿进行了配位交叉（CC），从而电荷密度从八面体转移到四面体网站和尖晶石结构，从而改变从逆到正常的压力增加和温度降低。CC的前体是在反尖晶石相的八面体位点内的d-电荷去耦。CC转变几乎完全发生在环境压力下的Verwey转变温度（TV= 122 K）。虽然TV随着压力而降低，但CC转变温度随着压力而升高，在10 GPa下达到350 K。由Verwey和后来由Mott提出的T<TVs的d电子局域化机制被证明与归因于Verwey转变的金属-绝缘体转变的实际机制无关。提出了一个一级相变发生在室温下的T> TV打开了一个小的间隙内的氧的p带，导致在观察到的绝缘状态在T>TV。
Temperature-dependent57Fe Mössbauer spectroscopy to 40 GPa shows that Fe3O4magnetite undergoes a coordination crossover (CC) whereby charge-density is shifted from octahedral to tetrahedral sites and the spinel structure thus changes from inverse to normal with increasing pressure and decreasing temperature. A precursor to the CC is a d-charge decoupling within the octahedral sites at the inverse spinel phase. The CC-transition takes place almost exactly at the Verwey transition temperature (TV=122K) at ambient pressure. While TVdecreases with pressure, the CC-transition temperature increases with pressure, reaching 350 K at 10 GPa. The d electron localization mechanism proposed by Verwey and later by Mott for T<TVis shown to be unrelated to the actual mechanism of the metal–insulator transition attributed to the Verwey transition. It is proposed that a first-order phase transition taking place at ∼TVat ambient pressure opens a small gap within the oxygen p-band, resulting in the observed insulating state at T>TV.