CO2-broken Ti–O bonds in the TiO6 octahedron of CaTiO3 for greatly enhanced room-temperature ferromagnetism

Abstract

Preparation of two-dimensional (2D) ferromagnetic nanomaterials and the study of their magnetic sources are crucial for the exploration of new materials with multiple applications. Herein, two-dimensional room-temperature ferromagnetic (FM) CaTiO₃ nanosheets are successfully constructed with the assistance of supercritical carbon dioxide (SC CO₂). In this process, the SC CO₂-induced strain effect can lead to lattice expansion and introduction of O vacancies. More importantly, experimentally it can be found out that the breakage of the Ti–O₂ bond by CO₂ directly results in the equatorial plane of the TiO₆ octahedron being exposed. This leads to more opportunities for oxygen vacancies and low-valent titanium to appear, where Ti³⁺ can optimize the spin structure, releasing the macroscopic magnetization. Greatly improved room-temperature ferromagnetic behavior, with an optimal magnetization of 0.1661 emu g⁻¹ and a high Curie temperature (Tc) of 300 K can be achieved.