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 (5.2−2 x )/6 Mn x /2 O 2 ( x = 0.0−0.4) nanosheets were synthesized by delaminating layered titanates [K 0.8 Ti (5.2−2 x )/3 Li (0.8− x )/3 Mn x O 4 ], 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 (5.2−2 x )/6 Mn x /2 O 2 ( 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 (5.2−2 x )/6 Mn x /2 O 2 ( x = 0.0−0.4) nanosheets exhibit a clear magnetic hysteresis loop at room-temperature in similar to what observed in ferromagnetic Ti 1− x Co x O 2 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 (5.2−2 x )/6 Mn x /2 O 2 was also employed to characterize the doping effect on electronic structures.