Unexpected structural and magnetic depth dependence of YIG thin films

Abstract

We report measurements on yttrium iron garnet (YIG) thin films grown on both gadolinium gallium garnet (GGG) and yttrium aluminium garnet (YAG) substrates, with and without thin Pt top layers. We provide three principal results: the observation of an interfacial region at the Pt/YIG interface, we place a limit on the induced magnetism of the Pt layer and confirm the existence of an interfacial layer at the GGG/YIG interface. Polarised neutron reflectometry (PNR) was used to give depth dependence of both the structure and magnetism of these structures. We find that a thin film of YIG on GGG is best described by three distinct layers: an interfacial layer near the GGG, around 5 nm thick and non-magnetic, a magnetic 'bulk' phase, and a non-magnetic and compositionally distinct thin layer near the surface. We theorise that the bottom layer, which is independent of the film thickness, is caused by Gd diffusion. The top layer is likely to be extremely important in inverse spin Hall effect measurements, and is most likely Y 2 O 3 or very similar. Magnetic sensitivity in the PNR to any induced moment in the Pt is increased by the existence of the Y 2 O 3 layer; any moment is found to be less than 0.02 uB/atom.

Interfacial Dzyaloshinskii-Moriya interaction arising from rare-earth orbital magnetism in insulating magnetic oxides

“…Complementary electron energy loss spectroscopy (EELS) is shown in Fig. 1d, e, revealing an interface region between the substrate and TmIG of~1 nm width where Gd and Ga have diffused into the TmIG layer, similar to other studies [30][31][32][33] . Perpendicular magnetization in all films is confirmed by vibrating sample magnetometry, shown in Fig.…”

Magnetic properties and domain structure of ultrathin yttrium iron garnet/Pt bilayers

“…The smaller diffusion range at the YIG/Pt interface is consistent with the low power and lower deposition temperature (room temperature) of Pt compared to the deposition of YIG on GGG. The moderate diffusion of Ga and Gd into the YIG film is also in agreement with previous reports 29,39 . The EELS analysis, shown in Fig.…”

Low damping and microstructural perfection of sub-40nm-thin yttrium iron garnet films grown by liquid phase epitaxy

“…4(h). In addition, the Gd diffusion in YIG films, as discussed for RF-magnetron sputtered [76,99] or PLD films [98], could lead to the incorporation of paramagnetic ions into the diamagnetic rare earth sublattice sites, which would also alter the magnetization [98]. However, no extended interdiffusion layer was observed at the film/substrate interface for our LPE films, so that the presence of a 'separate, abrupt' gadolinium iron garnet interface layer, as reported by Ref.…”