Room-Temperature Ferromagnetic Ultrathin α-MoO₃:Te Nanoflakes.

Abstract

We materialized room-temperature ferromagnetism in ultrathin α-MoO₃:Te nanoflakes. The α-MoO₃:Te nanoflakes, which had been grown by vapor-phase epitaxy, clearly exhibited an A_g Raman band from symmetric stretching of υ(Mo-O₃-Mo) in the 2D-like ultrathin α-MoO₃:Te layer. Due to the intentional incorporation of smaller Te ions into bigger Mo sites, the pentacoordinated Mo⁵⁺ bonds were created inside the orthorhombic α-MoO₃:Te lattice system. Since Mo⁵⁺ ions have magnetic moments from unpaired electron spins, a large number of overlapped bound magnetic polarons could be formed <i>via</i> ferromagnetic coupling with charged oxygen vacancies that are inevitably generated at pentacoordinated [Mo⁵⁺O₅] centers. This gives rise to the increase in long-range ferromagnetic ordering and leads to room-temperature ferromagnetism in the entire α-MoO₃:Te solid-state system. The results may move a step closer to the demonstration of spin functionalities in the wide bandgap semiconductor α-MoO₃:Te.