Substrate induced magnetic anisotropies and magneto-optical response in YIG nanosized epitaxial films on NdGG(111)

Nanosized Y3Fe5O12 epitaxial films have been grown on Nd3Ga5O12 substrates using laser molecular beam epitaxy method. Magneto-optical polar Kerr effect, ferromagnetic resonance and spin wave propagation measurements show that the stress-related anisotropy field has an opposite sign, compared to that in the YIG/GGG systems. This leads to a considerable decrease of the effective magnetization that opens a perspective to get YIG films with perpendicular magnetization for utilizing forward volume spin waves. Longitudinal magnetooptical Kerr effect magnetometry reveals a large contribution of quadratic in magnetization terms into dielectric permittivity tensor at optical frequencies. This effect strongly increases with temperature decrease and is explained by magnetization of the interface Nd ions that are exchange coupled to the Fe ions. The nanoscale heterostructures based on yttrium iron garnet (YIG, Y3Fe5O12) films attract much attention nowadays owing to the intense development of oxide spintronics and magnonics , , , . For the realization of effective data transmission and processing by spin wave packets, one needs high quality heterostructures with low magnetic losses at GHz frequencies. A great number of recent studies has been dedicated to investigation of epitaxial growth, static and dynamic magnetic properties of YIG layers epitaxially grown onto gadolinium gallium garnet (GGG, Gd3Ga5O12) substrates. The nanosized YIG films grown by laser molecular beam epitaxy (LMBE) exhibit high crystalline quality , , , , narrow-line ferromagnetic resonance (FMR) and low spin wave damping 9 , , , , . Assuming that the damping parameter α is linear function of the resonance frequency, in Ref. 10 it was calculated that α = 6.15×10. On the other hand, the direct measurement of spin wave propagation in nanosized YIG films grown at low temperatures (700 °C) shows that the damping parameter can be even lower (< 3.6⋅10) . In the absence of external magnetic field, the magnetization in YIG / GGG(111) films lies inplane due to the demagnetizing field Hd = 4πMs ≈ (1.2 – 1.5) kOe reinforced by the magnetic anisotropy Ha ≈ -1 kOe (4πMeff = 4πMs – Ha ≈ 2 kOe) induced by the magnetoelastic interactions 14 ,. In the forward volume spin wave devices the out-of-plane magnetization is necessary , , 18 and a strong permanent magnet is required. The way to avoid the bulky magnet, is to construct