Abstract
High quality epitaxial (111) Y3Fe5O12 (YIG) films are fabricated by annealing amorphous precursor films that are sputtering deposited on three kinds of single crystal garnet substrates with lattice constants exceeding that of YIG by a ratio from 0.76% to 1.58%. The effective perpendicular magnetic anisotropy (PMA) in the YIG films is significantly altered by the epitaxial strain induced magnetoelastic anisotropy. Large PMA is demonstrated in the fully strained thin YIG films on substrates with lattice mismatch from 1.05% to 1.58% due to the overwhelming of the magnetoelastic anisotropy. Less-strained YIG films, corresponding to partial strain relaxation at larger YIG thickness or smaller substrate lattice mismatch at 0.76%, show substantial but insufficient magnetoelastic anisotropy to overcome shape anisotropy. Magnetotransport characterization on YIG/Pt bilayers shows that the surface of YIG with either in-plane or perpendicular magnetization allows efficient equilibrium and/or nonequilibrium spin interexchange across the heterostructure interface.
Highlights
The development of YIG films with large perpendicular magnetic anisotropy (PMA) seems to be more challenging
To acquire robust PMA in high quality pure YIG thin films, in this paper, we have systematically investigated the structural and magnetic properties of thin epitaxial YIG films fabricated by annealing the amorphous precursor films on three kinds of the substituted garnet single crystal substrates
We have observed that the effective perpendicular magnetic anisotropy of the YIG films is significantly altered by the epitaxial strain induced magnetoelastic anisotropy, which strongly depends on the lattice mismatch ratio and film thickness
Summary
The development of YIG films with large PMA seems to be more challenging. So far, doping YIG in combination with epitaxial strain control has been reported to generate large PMA, i.e., Y3(Fe5−xMnx)O12 (Mn:YIG) on GGG,28 and (BixY3−x)Fe5O12 (Bi:YIG) on GGG and on substituted GGG substrates.29 Only a rather gentle PMA (effective PMA field of about 100–300 Oe) has been acquired in 10–20 nm pure YIG films grown in situ on substituted GGG substrates via a Sm3Ga5O12 (SmGG) buffer layer by using PLD.30 Parenthetically, Wang et al reported significant negative and positive magnetoelastic anisotropy contribution for YIG films sputtering deposited in situ on Y3Al5O12 and on substituted GGG with compressive and tensile strain, respectively, but the positive magnetoelastic anisotropy was insufficient to overcome the large negative shape anisotropy.31 The above results suggest that magnetoelastic anisotropy induced by epitaxial strain is still an effective way to tune the magnetic anisotropy of YIG films it is less efficient than that for TmIG, EuIG, and TbIG films. We have observed that the effective perpendicular magnetic anisotropy of the YIG films is significantly altered by the epitaxial strain induced magnetoelastic anisotropy, which strongly depends on the lattice mismatch ratio and film thickness.
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