Jiao Feng, Harrison Andrew, Jumas Jean-Claude, Chadwick Alan V, Kockelmann Winfried, Bruce Peter G
School of Chemistry and EaStChem, University of St. Andrews, UK.
J Am Chem Soc. 2006 Apr 26;128(16):5468-74. doi: 10.1021/ja0584774.
Alpha-Fe(2)O(3) has been synthesized with an ordered mesoporous structure and crystalline walls that exhibit a near-single crystal-like order. The unique magnetic behavior of the material, distinct from bulk nanoparticles of alpha-Fe(2)O(3) or mesoporous Fe(2)O(3) with disordered walls, has been established. Magnetic susceptibility, Mössbauer, and neutron diffraction data show that the material possesses the same long-range magnetic order as bulk alpha-Fe(2)O(3), despite the wall thickness being less than the 8 nm limit below which magnetic ordering breaks down in nanoparticulate alpha-Fe(2)O(3), yet the Morin transition of bulk alpha-Fe(2)O(3) is absent. It is also shown by TEM, PXRD, and EXAFS that alpha-Fe(2)O(3) with the same ordered mesoporous structure but disordered walls contains small crystalline domains. Mössbauer and magnetic susceptibility data demonstrate that this material exhibits no long-range magnetic order but superparamagnetic behavior.
α-Fe₂O₃已被合成出具有有序介孔结构和结晶壁的材料，其结晶壁呈现出近乎单晶状的有序性。该材料独特的磁行为已得到证实，这与块状α-Fe₂O₃纳米颗粒或壁无序的介孔Fe₂O₃不同。磁化率、穆斯堡尔谱和中子衍射数据表明，尽管壁厚度小于8nm（在纳米颗粒α-Fe₂O₃中，低于此极限磁有序会被破坏），但该材料仍具有与块状α-Fe₂O₃相同的长程磁有序，不过块状α-Fe₂O₃的莫林转变不存在。透射电子显微镜（TEM）、粉末X射线衍射（PXRD）和扩展X射线吸收精细结构（EXAFS）也表明，具有相同有序介孔结构但壁无序的α-Fe₂O₃包含小的结晶域。穆斯堡尔谱和磁化率数据表明，这种材料没有长程磁有序，而是表现出超顺磁性行为。
