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

Abstract

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.

Stress-Induced Magnetic Properties of Gadolinium Iron Garnet Nanoscale-Thin Films: Implications for Spintronic Devices

“…Note that a small compressive out-of-plane strain is expected for GdIG/GYSGG films, but a small tensile strain was observed. For garnets grown at low oxygen pressure, oxygen vacancies can lead to changed lattice parameters, − and could therefore cause a reduced tensile strain for films grown on GSGG or even compressive strain in films grown on GYSGG substrates. However, while a recent report showed strong implications on the structural and magnetic parameters of YIG thin films with intentionally introduced oxygen vacancies, this effect is believed to be small for PLD grown films .…”

“…For garnets grown at low oxygen pressure, oxygen vacancies can lead to changed lattice parameters, − and could therefore cause a reduced tensile strain for films grown on GSGG or even compressive strain in films grown on GYSGG substrates. However, while a recent report showed strong implications on the structural and magnetic parameters of YIG thin films with intentionally introduced oxygen vacancies, this effect is believed to be small for PLD grown films . Additionally, a slight off-stoichiometry in the grown films can give rise to a changed lattice parameter as well.…”

“…However, while a recent report showed strong implications on the structural and magnetic parameters of YIG thin films with intentionally introduced oxygen vacancies, this effect is believed to be small for PLD grown films. 47 Additionally, a slight off-stoichiometry in the grown films can give rise to a changed lattice parameter as well. A composition series presented later in this work shows that already an offstoichiometry of around ±2% leads to a decreased film strain.…”