A group pf scientists have quantified the nanometer-thick Y3Fe5O12 (YIG) films epitaxially grown on Gd3Ga5O12 (GGG) with a magnetic dead layer as thin as about 1.2？nm by polarized neutron reflectivity and magnetization measurements.
They found that vacuum annealing on YIG at 300–400？°C leads to substantial reduction in the anomalous Hall effect, spin Hall magnetoresistance, and spin pumping in YIG/Pt bilayers but causes large enhancement in the spin Seebeck effect. The structural, static, and dynamic magnetic measurements show that the annealing has no discernible influence on the global oxidization states and saturation magnetization of YIG films but introduces subtle defects possibly in the form of oxygen vacancies.
This study suggests that subtle defects in thin YIG films have multiple effects on the spin transport properties, and caution should be taken in annealing YIG in vacuum. It opens up a new way to improve longitudinal spin Seebeck effect for applications in spin caloritronic devices. Further experimental work and quantitative theoretical calculations are needed to interpret these findings in depth.
The full publication can be found here: https://aip.scitation.org/doi/10.1063/1.5124832