Interface magnetization in Y3Fe5O12 / Nd3Ga5O12 epitaxial heterostructures caused by Fe3+- Nd3+ exchange coupling

The spectral and magnetic field dependences of the polar magneto-optical Kerr effect (PMOKE) were studied in heterostructures formed by 10 - 40 nm Y3Fe5O12 (YIG) layer grown by laser molecular beam epitaxy on Nd3Ga5O12 (NdGG) and Gd3Ga5O12 (GGG) substrates. The PMOKE spectra can be decomposed into two components, one of which, caused by the Faraday effect in the substrate, is linear in magnetic field H, and the second is saturated at H similar to 0,04 - 0,056 MA/m. In YIG / NdGG, the spectral dependence of the substrate-caused PMOKE clearly reveals a series of narrow bands corresponding to electronic transitions (absorption bands) in the Nd3+ ion. The saturable component of PMOKE, which reflects the behavior of the magnetization of the YIG film, is similar to that observed in YIG / GGG, but at the same time clearly reveals anomalies at the photon energies, corresponding to electronic transitions in the Nd3+ ion. This indicates the presence of magnetization of Nd3+ ions in the interface region of the YIG / NdGG structure, induced by the exchange interaction Nd3+ - Fe3+. The signs of the PMOKE anomalies and possible influence of NdGG substrate complex refractive index on PMOKE caused by YIG film are discussed.