Absence of a ferromagnetic phase in pure Ge quantum dots and Ge/SiO2 multilayer films

Quantum magnetism is currently one of the most challenging areas of materials science. Research efforts have been concentrated on studying the onset or the nano-scale systems that are originally nonmagnetic in bulk forms. Recently, claims of the existence of Ge-based ferromagnetism in pure Ge quantum dots and Ge/SiO2 multilayer films have attracted certain attention from the scientific world. However, if both Ge quantum dots and Ge/SiO2 multilayer films were able to form ordered magnetic states without the contribution of extrinsic inclusions, the induced ferromagnetism would be certainly incompatible with our knowledge of magnetism in physics. We therefore reinitiate an investigation in order to examine the validity of their claims. Unfortunately, our results have shown that neither pure Ge quantum dots nor Ge/SiO2 multilayer films were able to exhibit ferromagnetism. The ferromagnetism of the "ferromagnetic Ge" was most likely originated from contaminants, such as Fe and Ni and not from Ge. (C) 2014 Elsevier B.V. All rights reserved.