Unusual anomalous Hall effect in perpendicularly magnetized YIG films with a small Gilbert damping constant

Abstract

The ${\mathrm{Y}}_{3}\mathrm{F}{\mathrm{e}}_{5}{\mathrm{O}}_{12}$ (YIG) films with perpendicular magnetic anisotropy (PMA) have recently attracted a great deal of attention for spintronics applications. Here, we report the induced PMA in the YIG films grown on $(\mathrm{G}{\mathrm{d}}_{2.6}\mathrm{C}{\mathrm{a}}_{0.4})(\mathrm{G}{\mathrm{a}}_{4.1}\mathrm{M}{\mathrm{g}}_{0.25}\mathrm{Z}{\mathrm{r}}_{0.65}){\mathrm{O}}_{12}$ (SGGG) substrates by epitaxial strain without preprocessing. Reciprocal space mapping shows that the films are lattice matched to the substrates without strain relaxation. Through ferromagnetic resonance and polarized neutron reflectometry measurements, we find that these YIG films have an ultralow Gilbert damping constant ($\ensuremath{\alpha}l1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$) and a magnetic dead layer, which is negligible at the YIG/SGGG interfaces. Moreover, the transport behavior of Pt/YIG/SGGG films reveals an enhancement of spin mixing conductance and a large unusual anomalous Hall effect (UAHE) as compared with $\mathrm{Pt}/\mathrm{YIG}/\mathrm{G}{\mathrm{d}}_{3}\mathrm{G}{\mathrm{a}}_{5}{\mathrm{O}}_{12}$ (GGG) films. Although the UAHE in Pt/YIG/SGGG films show different characteristics with varying YIG thickness, they are all ascribed to the possible noncollinear magnetic order at the Pt/YIG interfaces induced by epitaxial strain.