论文标题
纳米厚度微光磁铁矿晶体的Verwey过渡中的尺寸效应
Size effects in the Verwey transition of nanometer-thick micron-wide magnetite crystals
论文作者
论文摘要
我们使用拉曼光谱法监测了在Al2O3（0001）上的纳米厚磁铁矿岛上的VERWEY过渡。这些岛屿是由高温氧辅助分子束外延生长的。低于100 k，对于20 nm以上的厚度，拉曼光谱对应于在散装晶体中观察到的，以及用于亚弗威磁铁矿结构的高质量薄膜。在室温下，立方相模式的宽度与散装晶体中报告的最佳报道相似，表明电子 - phonon相互作用水平相似。拉曼光谱在冷却时的演变表明，对于比20 nm厚的岛屿，结构性变化首先在150 K开始时出现在温度下，而Verwey过渡本身在115 K左右发生。但是，岛屿比20 nm的岛屿较薄，表现出截然不同
We have monitored the Verwey transition in micrometer-wide, nanometer-thick magnetite islands on epitaxial Ru films on Al2O3(0001) using Raman spectroscopy. The islands have been grown by high-temperature oxygen-assisted molecular beam epitaxy. Below 100 K and for thicknesses above 20 nm the Raman spectra correspond to those observed in bulk crystals and high quality thin films for the sub-Verwey magnetite structure. At room temperature the width of the cubic phase modes is similar to the best reported in bulk crystals, indicating a similar level of electron-phonon interaction. The evolution of the Raman spectra upon cooling suggests that for islands thicker than 20 nm, structural changes appear first at temperatures starting at 150 K and the Verwey transition itself takes place at around 115 K. However, islands thinner than 20 nm show a very different Raman spectra indicating that while a transition takes place, the charge order of the ultrathin islands differs markedly from their thicker counterparts
