Magnetic Domain Structure of Lu2.1Bi0.9Fe5O12 Epitaxial Films Studied by Magnetic Force Microscopy and Optical Second Harmonic Generation

Abstract

Magnetic structure of functional magnetic dielectrics is traditionally of high interest. Here, we use the magnetic force microscopy (MFM) and nonlinear-optical probe of second harmonic generation for studies of surface domain structure of monocrystalline Lu2.1Bi0.9Fe5O12 garnet films. The transformation of the magnetic domains under the application of the dc magnetic field is revealed by the MFM for both the top-view and the cleavage of the iron-garnet layer. Complementary magnetic force and second harmonic generation microscopy show that the considered film reveals the magnetization inclined with respect to the film’s normal, with its orientation being inhomogeneous within the film’s thickness. The second harmonic generation (SHG) microscopy confirms the zigzag structure of the surface-closing domain with the magnetization containing in-plane and out-of-plane magnetization components. We believe that these features of magnetic behavior of garnet films are important for the design of garnet-based magnetic devices.

Third harmonic generation microscopy of magnetic domains in garnet films

“…As stems from the analysis of the THG and SHG microscopy patterns obtained for different combinations of polarizations of the pump and harmonics' waves, the inplane average orientation of magnetization in these interface domains differs from that of the bulk stripe ones. The average magnetization in adjacent surface domains forms an angle smaller than π, which also correlates with our previous magnetic force microscopy (MFM) results [19,20].…”

“…The THG intensity patterns measured for the perpendicular polarizations of the fundamental and THG beams reveal the presence of magnetic stripe domains, which indicates the presence of both even and odd in M components of the THG polarization in that case. This means that the magnetization of the stripe domains is inclined with respect to the domain axis in appliance with our previous studies of similar garnet films by means of the SHG microscopy [19,20]. The presence of the symmetry forbidden crystallographic THG components in that case can be due to a small misalignment of the polarization plane of the pump beam, a possible reason for this can be the linear Faraday rotation of the fundamental beam.…”

“…In our experiments a high in-depth resolution of the THG microscopy originates from the small THG radiation depth governed by a strong garnet absorption at the third harmonic wavelength. This allows to apply the THG probe for the studies of magnetic structures at interfaces similarly to demonstrated previously for the case of SHG [19] .…”

“…Speaking about the nonlinear optical microscopy, it was SHG that was first applied for the visualization and studies of magnetically ordered crystals [16][17][18]. Recently, the organization of magnetic domains at the surface and buried interface of epitaxial garnet films was studied by the SHG microscopy [19,20]. Concerning the THG microscopy of magnetic structures, the research progress is more modest; it was shown that magneto-optical effects at the THG wavelength are comparable to linear optical ones in nanostructured ferromagnetic metals [7], garnet-based films [21,22] and magnetophotonic microcavities [23].…”

Nonlinear Optical Microscopy of Interface Layers of Epitaxial Garnet Films

“…Recently it was shown that the SHG microscopy can distinguish stripe domains in the bulk of garnet films, as well as the closure domains at the outer garnet/air interface [42]. At the same time, the domain structure of the hidden interface of the ferrimagnetic film with the substrate remained unexplored.…”