Structural, Magnetic, and Low-Temperature Electrical Transport Properties of YIG Thin Films with Heavily Reduced Oxygen Contents

Yttrium–iron–garnet (YIG) is attracting a lot of interest due to its applications in spintronic devices. Previous reports have shown that oxygen content is essential for tuning the structural and magnetic properties of YIG films. However, the effect was not remarkable due to the small change of oxygen content. It is interesting to explore the properties of YIG with greatly reduced oxygen contents, which has not been reported so far. Here we report on YIG thin films with heavily reduced oxygen contents via annealing with graphite, and their structural, magnetic, and electrical transport properties. Both the saturation magnetization and lattice parameter of the samples decrease with reduced oxygen content. Moreover, electrical resistivity can be reduced up to several orders of magnitude, so the low-temperature electrical transport properties of YIG thin films are studied for the first time. The electrical transport is dominated by the thermal activation behavior above 100 K. While below 100 K, it shows Mott-variable range hopping conduction for the 570 °C annealed sample and tunneling conduction for the other samples. This work indicates dramatic changes of properties for YIG with heavily reduced oxygen contents and paves the way for tuning other materials with oxygen content.