Ordered mesoporous Fe2O3 with crystalline walls

alpha-Fe2O3 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-Fe2O3 or mesoporous Fe2O3 with disordered walls, has been established. Magnetic susceptibility, Mossbauer, and neutron diffraction data show that the material possesses the same long-range magnetic order as bulk alpha-Fe2O3, despite the wall thickness being less than the 8 nm limit below which magnetic ordering breaks down in nanciparticulate alpha-Fe2O3, yet the Morin transition of bulk alpha-Fe2O3 is absent. It is also shown by TEM, PXRD, and EXAFS that alpha-Fe2O3 with the same ordered mesoporous structure but disordered walls contains small crystalline domains. Mossbauer and magnetic susceptibility data demonstrate that this material exhibits no long-range magnetic order but superparamagnetic behavior.