1 research outputs found
Large-Pore Mesoporous Ho<sub>3</sub>Fe<sub>5</sub>O<sub>12</sub> Thin Films with a Strong Room-Temperature Perpendicular Magnetic Anisotropy by Sol–Gel Processing
We
report the evaporation-induced self-assembly synthesis of large-pore
mesoporous thin films of ferrimagnetic holmium iron garnet (Ho<sub>3</sub>Fe<sub>5</sub>O<sub>12</sub>) from nitrate salt precursors
and a polyisobutylene-<i>block</i>-polyÂ(ethylene oxide)
polymer structure-directing agent. The phase composition, atomic bonding
configuration, and pore structure of the top surface and the interior
of the films were investigated by microscopy, scattering, and spectroscopy
techniques, including synchrotron-based grazing incidence small-angle
X-ray scattering, X-ray photoelectron spectroscopy, X-ray diffraction
(including Rietveld refinement), and others. The data provide evidence
that the sol–gel-derived material is single-phase garnet with
27 nm diameter crystallites and few defects after being heated to
850 °C in air, and the continuous network of pores averaging
23 nm in diameter is preserved to a large extent, despite a solid–solid
conversion from metastable <i>h</i>-HoFeO<sub>3</sub> to
Ho<sub>3</sub>Fe<sub>5</sub>O<sub>12</sub> during the crystallization
process. Furthermore, dc magnetometry measurements show the thin films
are magnetically stable with a room-temperature coercivity of ∼170
Oe and exhibit an out-of-plane easy axis with a significant perpendicular
magnetic anisotropy. A strong preference for out-of-plane magnetic
alignment in solution-processed mesostructured films is unique, making
them attractive for application in spintronics and nanomagnetics