Department of Chemistry, KAIST, Daejeon 305-701, Korea.
J Am Chem Soc. 2010 Dec 15;132(49):17447-51. doi: 10.1021/ja104189p. Epub 2010 Nov 18.
Single-crystalline free-standing hexagonal Fe(1.3)Ge nanowires (NWs) are synthesized for the first time using a chemical vapor transport process without using any catalyst. Interestingly, Fe(1.3)Ge NWs are found to be ferromagnetic at room temperature, while bulk Fe(1.3)Ge has the lower critical temperature of 200 K. We perform first-principles density functional calculations and suggest that the observed strong ferromagnetism is attributed to the reduced distances between Fe atoms, increased number of Fe-Fe bonds, and the enhanced Fe magnetic moments. Both experimental and theoretical studies show that the magnetic moments are enhanced in the NWs, as compared to bulk Fe(1.3)Ge. We also modulate the composition ratio of as-grown iron germanide NWs by adjusting experimental conditions. It is shown that uniaxial strain on the hexagonal plane also enhances the ferromagnetic stability.
首次使用化学气相输运工艺，在不使用任何催化剂的情况下，合成出单晶、独立的六方结构 Fe(1.3)Ge 纳米线 (NWs)。有趣的是，室温下发现 Fe(1.3)Ge NWs 具有铁磁性，而块状 Fe(1.3)Ge 的临界温度低至 200 K。我们进行了第一性原理密度泛函计算，并提出观察到的强铁磁性归因于 Fe 原子之间的距离减小、Fe-Fe 键数量增加以及 Fe 磁矩增强。实验和理论研究都表明，与块状 Fe(1.3)Ge 相比，NWs 中的磁矩增强。我们还通过调整实验条件来调制生长的铁锗化物 NWs 的组成比。结果表明，六方平面上的单轴应变也增强了铁磁性稳定性。
