Title of Presentation
Characterization of the Magnetic Phase in Ti-Doped Vanadium Dioxide
Date of Presentation
Name of Conference
Conference for Undergraduate Women in Physics - American Physical Society
Date of Conference
Location of Conference
Here we present a characterization of the recently discovered magnetic phase in titanium-doped vanadium dioxide (VO2:Ti with 1, 3 & 5 at%) via Muon Spin Relaxation (MuSR) measurements. Specifically, variations in the magnetic phase were studied as a function of titanium dopant concentration in an effort to understand the fundamental mechanism responsible for magnetism and other transitions exhibited by the material.
Muons are spin 1/2 particles with an average lifetime of 2.2 us and a gyromagnetic ratio of 135.54 MHz/T that are used to study the local magnetic environment through a technique known as Muon Spin Relaxation/Rotation/Resonance (MuSR). Implanted muons precess about the field in their local environment until they decay into a positron that is preferentially aligned with the spin direction at the time of decay (and associated neutrinos). By tracking these positrons, the time evolution of the muon spin polarization is determined and used to map the local magnetic field distribution at the muon stopping site. VO2 exhibits an ultra-fast, reversible metal−semiconductor transition (MST) at TMST near 340 K. Above TMST it is metallic, reflective and electrically conductive; below, the electrical conductivity drops by several orders of magnitude, it is transparent with a bandgap of 0.7 eV. The MST can be triggered by thermal, optical, electrical or barometric means and is accompanied by a structural transition. Dopants like tungsten and Ti reduce TMST to below room temperature while having minimal effect on the electronic or optical properties of the host, whereas dopants such as fluorine and chromium can raise it to above 400 K. While VO2 has been studied since the 1960s, its low-temperature magnetic phase was first reported in 2014 by our collaboration. This contribution is part of a large-scale project aimed at understanding the fundamental mechanism responsible for transitions in VO2 compounds, a question still highly debated within the community.
Goeks, M R.; Mengyan, Patrick W.; and Lichti, R L., "Characterization of the Magnetic Phase in Ti-Doped Vanadium Dioxide" (2018). Conference Presentations. 350.