Abstract
Thin (4–20 nm) yttrium iron garnet (Y3Fe5O12, YIG) layers have been grown on gadolinium gallium garnet (Gd3Ga5O12, GGG) 111-oriented substrates by laser molecular beam epitaxy in 700–1000 °C growth temperature range. The layers were found to have atomically flat step-and-terrace surface morphology with step height of 1.8 Å characteristic for YIG(111) surface. As the growth temperature is increased from 700 to 1000 °C the terraces become wider and the growth gradually changes from layer by layer to step-flow regime. Crystal structure studied by electron and X-ray diffraction showed that YIG lattice is co-oriented and laterally pseudomorphic to GGG with small rhombohedral distortion present perpendicular to the surface. Measurements of magnetic moment, magneto-optical polar and longitudinal Kerr effect (MOKE), and X-ray magnetic circular dichroism (XMCD) were used for study of magnetization reversal for different orientations of magnetic field. These methods and ferromagnetic resonance studies have shown that in zero magnetic field magnetization lies in the film plane due to both shape and induced anisotropies. Vectorial MOKE studies have revealed the presence of an in-plane easy magnetization axis. In-plane magnetization reversal was shown to occur through combination of reversible rotation and abrupt irreversible magnetization jump, the latter caused by domain wall nucleation and propagation. The field at which the flip takes place depends on the angle between the applied magnetic field and the easy magnetization axis and can be described by the modified Stoner–Wohlfarth model taking into account magnetic field dependence of the domain wall energy. Magnetization curves of individual tetrahedral and octahedral magnetic Fe3+ sublattices were studied by XMCD.
Highlights
Yttrium iron garnet (YIG) is a model object for study of magnetism in crystals
The role of gadolinium gallium garnet (GGG) substrate annealing prior to YIG growth becomes evident from analysis of atomic force microscopy (AFM) surface morphology images measured before and after 1000 °C annealing in oxygen (Figure 2(a) and 2(b))
AFM images presented in Figure 2(c) and 2(d) show such step-and-terrace morphology for the YIG layers grown at 1000 and 850 °C illustrating the dependence of characteristic terrace width on the growth temperature
Summary
Dynamic, magnetic and magneto-optical properties of such films have been carried out [1,3,4,9]. Investigations into structural, magneto-optical, static and dynamic magnetic properties of such layers have been reported [27,28,29,30,31,32,33,34,35,36,37]. The aim of the present work is to grow YIG layers by laser MBE, to characterize their structural properties and to study mechanisms responsible for magnetization reversal in the in-plane and out-of-plane magnetic fields.
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