The Distortion-Adjusted Change of Thermal Expansion Behavior of Cubic Magnetic Semiconductor (Sc_1−xM_x)F₃ (M = Al, Fe)

For the study of negative thermal expansion (NTE) compounds, it is critical to effectively control the thermal expansion. In this letter, a chemical approach has been taken to control the thermal expansion behavior in ScF₃ which has a strong NTE. Owing to the difference of radius of substituting ions, local distortion inevitably emerges in the lattice matrix, which is verified by pair distribution function analysis of high-resolution synchrotron X-ray scattering. It is a valuable clue that the thermal expansion behaviors in the ScF₃ based systems and other trifluorides are correlated closely to structural distortion of metal-F-metal linkages. In addition, the introduction of 3d transition-metal enables its semiconductor and ferromagnetic characteristics. This study provides important reference opinion for the control of thermal expansion and introduction of multifunctionalization for those NTE compounds with open framework structure.