Kim Taehun, Sim Sangwoo, Lim Sumin, Patino Midori Amano, Hong Jaeyoung, Lee Jisoo, Hyeon Taeghwan, Shimakawa Yuichi, Lee Soonchil, Attfield J Paul, Park Je-Geun
Center for Quantum Materials, Seoul National University, Seoul, 08826, Republic of Korea.
Department of Physics and Astronomy, Seoul National University, Seoul, 08826, Republic of Korea.
Nat Commun. 2021 Nov 4;12(1):6356. doi: 10.1038/s41467-021-26566-4.
Magnetite (FeO) is of fundamental importance for the Verwey transition near T = 125 K, below which a complex lattice distortion and electron orders occur. The Verwey transition is suppressed by chemical doping effects giving rise to well-documented first and second-order regimes, but the origin of the order change is unclear. Here, we show that slow oxidation of monodisperse FeO nanoparticles leads to an intriguing variation of the Verwey transition: an initial drop of T to a minimum at 70 K after 75 days and a followed recovery to 95 K after 160 days. A physical model based on both doping and doping-gradient effects accounts quantitatively for this evolution between inhomogeneous to homogeneous doping regimes. This work demonstrates that slow oxidation of nanoparticles can give exquisite control and separation of homogeneous and inhomogeneous doping effects on the Verwey transition and offers opportunities for similar insights into complex electronic and magnetic phase transitions in other materials.
磁铁矿（FeO）对于在T = 125K附近的韦尔韦转变至关重要，低于该温度会出现复杂的晶格畸变和电子有序现象。韦尔韦转变会受到化学掺杂效应的抑制，从而产生有充分记录的一阶和二阶状态，但有序变化的起源尚不清楚。在此，我们表明单分散FeO纳米颗粒的缓慢氧化会导致韦尔韦转变出现有趣的变化：在75天后T最初降至70K的最小值，然后在160天后恢复到95K。基于掺杂和掺杂梯度效应的物理模型定量地解释了这种从非均匀掺杂状态到均匀掺杂状态的演变。这项工作表明，纳米颗粒的缓慢氧化可以对韦尔韦转变的均匀和非均匀掺杂效应进行精确控制和区分，并为深入了解其他材料中复杂的电子和磁相变提供了类似的机会。
