Synthesis of Mn-Substituted Titania Nanosheets and Ferromagnetic Thin Films with Controlled Doping

We report the synthesis of Mn-substituted titania nanosheets and the preparation of room-temperature ferromagnetic thin films via layer-by-layer assembly of these nanosheets. Ti(5.2−2x)/6Mnx/2O2 (x = 0.0−0.4) nanosheets were synthesized by delaminating layered titanates [K0.8Ti(5.2−2x)/3Li(0.8−x)/3MnxO4], in which the Mn content was systematically controlled by Li+ doping. We found that Mn content in the host layers was preserved upon exfoliation, and controlled Mn doping was achieved in exfoliated Ti(5.2−2x)/6Mnx/2O2 (x = 0.0−0.4) nanosheets, where Li+ ions were completely extracted by acid-exchange reaction in the exfoliation process. The multilayer films of Ti(5.2−2x)/6Mnx/2O2 (x = 0.0−0.4) nanosheets exhibit a clear magnetic hysteresis loop at room-temperature in similar to what observed in ferromagnetic Ti1−xCoxO2 nanosheets. Electronic absorption, magnetic circular dichroism, and hard X-ray photoelectron spectroscopy were used to identify Mn-derived states, and analyze the properties of these states related to ferromagnetism. The first-principles calculation of Ti(5.2−2x)/6Mnx/2O2 was also employed to characterize the doping effect on electronic structures.