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

• Published in: Journal of magnetism and magnetic materials 2014-08, Vol.363, p.108-113
• Main Authors: Chi, Y.C., Chao, J.H.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Magnetic properties and materials; Magnetic properties of nanostructures; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other interactions of matter with particles and radiation; Physics; Quantum dots; Room-temperature ferromagnetism; X-ray absorption and absorption edges
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2014.03.060

Quantum magnetism is currently one of the most challenging areas of materials science. Research efforts have been concentrated on studying the onset of the nano-scale systems that are originally non-magnetic 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. •We challenge the previous claims of intrinsic ferromagnetism in Ge nanostructures.•The results show that ferromagnetism is absent in their structures.•We suggest that the alleged ferromagnetism is originated from contaminants.•We provide a weighty refutation to the undoped ferro-candidates in question.