Nanocasting of Mesoporous In‐TM (TM = Co, Fe, Mn) Oxides: Towards 3D Diluted‐Oxide Magnetic Semiconductor Architectures

Abstract

Transition metal (Co, Fe, Mn)‐doped In2O3−y mesoporous oxides are synthesized by nanocasting using mesoporous silica as hard templates. 3D ordered mesoporous replicas are obtained after silica removal in the case of the In‐Co and In‐Fe oxide powders. During the conversion of metal nitrates into the target mixed oxides, Co, Fe, and Mn ions enter the lattice of the In2O3 bixbyite phase via isovalent or heterovalent cation substitution, leading to a reduction in the cell parameter. In turn, non‐negligible amounts of oxygen vacancies are also present, as evidenced from Rietveld refinements of the X‐ray diffraction patterns. In addition to (In1−xTMx)2O3−y, minor amounts of Co3O4, α‐Fe2O3, and MnxOy phases are also detected, which originate from the remaining TM cations not forming part of the bixbyite lattice. The resulting TM‐doped In2O3−y mesoporous materials show a ferromagnetic response at room temperature, superimposed on a paramagnetic background. Conversely, undoped In2O3−y exhibits a mixed diamagnetic‐ferromagnetic behavior with much smaller magnetization. The influence of the oxygen vacancies and the doping elements on the magnetic properties of these materials is discussed. Due to their 3D mesostructural geometrical arrangement and their room‐temperature ferromagnetic behavior, mesoporous oxide‐diluted magnetic semiconductors may become smart materials for the implementation of advanced components in spintronic nanodevices.

Co2+@Mesoporous Silica Monoliths: Tailor‐Made Nanoreactors for Confined Soft Chemistry

“…In order to use these remarkable ordered nanostructures in diverse applications, silica matrices have been functionalized with molecules17 or nanoparticles 18–22. They have also been used as hard templates that can precisely cast functional materials to form replicas23–26 or nanoparticles with controlled size and shape 18–22. Whereas the use of the ordered porosity as a hard template for the elaboration of nanoparticles generally involves a single step such as a thermal treatment, the development of confined chemistry remains limited by the difficulty of controlling the insertion, dispersion, and speciation of the reactants in the pores.…”

Design of Lead(II) Metal–Organic Frameworks Based on Covalent and Tetrel Bonding

“…[16] In order to use these remarkable ordered nanostructures in diverse applications, silica matrices have been functionalized with molecules [17] or nanoparticles. [18][19][20][21][22] They have also been used as hard templates that can precisely cast functional materials to form replicas [23][24][25][26] or nanoparticles with controlled size and shape. [18][19][20][21][22] Whereas the use of the ordered porosity as ah ard template for the elaboration of nanoparticles generally involves as ingle step such as at hermalt reatment, the development of confinedc hemistry remains limited by the difficulty of controlling the insertion, dispersion, and speciation of the reactants in the pores.…”

Nanocasting synthesis of mesoporous SnO2 with a tunable ferromagnetic response through Ni loading

“…22 Recently, Co-, Fe-and Mn-doped In 2 O 3 mesoporous powders have been reported to show room temperature ferromagnetic properties, hence constituting mesoporous oxidediluted magnetic semiconductors (MODMS). 23 Actually, since the prediction of room-temperature ferromagnetic (RTFM) response in Mn-doped ZnO, 24 great efforts have been devoted toward the preparation of oxide-diluted magnetic semiconductors by doping wide band gap semiconductors with transition metal cations. Many groups have reported the occurrence of RTFM in nanowires, 25,26 thin lms 27 and nanoparticles 28 by controllably doping semiconductor matrices made of TiO 2 , ZnO, In 2 O 3 and CaO with suitable transition metals.…”

“…The magnetic behavior of MODMS can be tuned by adjusting the transition metal doping level and the amount of oxygen vacancies. 23 Secondary phases (i.e., TM x O y where TM ¼ transition metal) were actually found to also play a role on the magnetic properties, even though the secondary phases are typically antiferromagnetic (AFM) transition metal oxides. Nonetheless, AFM materials are encountering a renewed interest in spintronics, beyond their use in spin valves or tunnelling junction architectures, as essential elements in spintransfer torque devices or encrypted magnetic memories.…”