Static and Dynamic Magnetic Properties of Single‐Crystalline Yttrium Iron Garnet Films Epitaxially Grown on Three Garnet Substrates

Abstract

sections. Yttrium iron garnet (YIG) is extensively used for SW devices [11][12][13] because of its low intrinsic Gilbert damping, [14][15][16][17][18][19] but other materials with low Gilbert damping have been proposed, including Permalloy [20,21] and Heusler alloys. [22] However, films of low anisotropy materials such as YIG and Permalloy are typically magnetized in plane due to the dominant shape anisotropy and require a substantial external outof-plane magnetic field to saturate the film. This motivates the search for a magnetic material with a low Gilbert damping and a low out-of-plane saturation field, or ideally with a perpendicular magnetic anisotropy (PMA) that promotes an out-of-plane remanent magnetization, in order to realize integrated FV SW devices.The net magnetic anisotropy includes contributions from magnetocrystalline anisotropy, magnetoelastic anisotropy, and shape anisotropy. [9] In epitaxial films, magnetoelastic anisotropy can be tuned via the lattice mismatch with the substrate. Although YIG has only a modest magnetostriction, PMA was reported for 20 nm thick epitaxial YIG on a Sm 3 Ga 5 O 12 (SmGG) buffer layer on a rare-earth-substituted gadolinium gallium garnet (SGGG) substrate and for SGGG/SmGG/40 nm thick YIG/SmGG, [23] in which the top SmGG suppresses strain relaxation. The top SmGG was essential to obtain PMA in >40 nm thick YIG, but such overlayers lead to spacing loss which would decrease the efficiency of SW excitations using an antenna. Seed and buffer layers also lead to a more complex growth and patterning process. PMA has also been obtained in several single-layer rare-earth-substituted garnet films as a result of magnetoelastic anisotropy, [24][25][26][27] but the substitution of rare earth ions for Y in the iron garnet system tends to increase the Gilbert damping. [28,29] In these reports, there were no detailed discussions of the relation between the magnetoelastic anisotropy and the propagation properties of FV SWs.In this work, the effect of epitaxial mismatch on the net anisotropy and damping of YIG is described. By changing the magnetoelastic anisotropy, the field required for saturating the YIG out of plane can be reduced, facilitating the development of FV SW devices. Three epitaxial YIG films were prepared on gadolinium gallium garnet (GGG), SGGG, and neodymium gallium garnet (NGG) substrates directly (without any buffer layers). These substrates have the same crystalline structure but different lattice constants, yielding different lattice strain and Single-crystalline yttrium iron garnet (YIG) films are grown on gadolinium gallium garnet (GGG), rare-earth-substituted GGG, and neodymium gallium garnet (NGG) substrates, and their crystalline structures, surface morphologies, magnetic and magneto-optical properties, spin wave (SW) spectra of the forward volume (FV) mode, and damping parameters are characterized. YIG grown on NGG shows the smallest out-of-plane effective anisotropy field of 1080 Oe among the three samples because of its larger magnetoelastic anisotropy...

Three port logic gate using forward volume spin wave interference in a thin yttrium iron garnet film

“…The unit cell volume of this rhombohedral lattice was 1.9628 nm 3 (). These values were similar to those used in our previous studies 76 . X-ray reflectometry (XRR) measurements showed that the films had a smooth surface with an average roughness, R a , of 0.47 nm and exhibited a density, ρ , of 5.17 g cm −3 (see Fig.…”

“…The propagation of SWs in the film was characterized as described in a previous article 76 . Six pairs of antennas with various spacings were fabricated on the YIG film, and transmittance of signals between each pair of antennas was measured using a vector network analyzer (VNA).…”

“…The measured intensity was plotted as a function of propagation length, yielding the attenuation length L att at which the SW intensity decayed by a factor 1/e. The value of L att was converted to the net damping parameter α SW which includes the extrinsic damping using 1,76 where , , , and . Here f , k , d , γ , , , and represent the frequency, the wavenumber, the YIG thickness, the gyromagnetic ratio ( = 2.8 MHz/Oe for YIG), the effective magnetic field, the applied magnetic field, and the net magnetic anisotropy field obtained from spin wave spectroscopy (SWS, described in the following section).…”

Interfacial and Bulk Magnetic Properties of Stoichiometric Cerium Doped Terbium Iron Garnet Polycrystalline Thin Films

“…Investigations on garnet interfaces have been confined to epitaxial garnet films on gadolinium gallium garnet (GGG). [ 14–16 ] Jakubisova et al attributed the anomaly in MO polar Kerr rotation in nm‐thick yttrium iron garnet (YIG) on GGG (111) to the presence of a transition layer with opposite Fe 3+ sublattice magnetization that is antiferromagnetically coupled to the dodecahedral Gd 3+ in the substrate. [ 17 ] In other research, the formation of a magnetically compensated layer from the interdiffusion of Fe from the film and Gd‐Ga from the substrate is suggested as a result of high temperature annealing.…”

Role of gallium diffusion in the formation of a magnetically dead layer at the Y3Fe5O12/Gd3Ga5Korovin1, Bursian2, Lutsev3 et al. 2018Phys. Rev. Materials482130View full textAdd to dashboardCite

“…The intense interest in nanometer-scale epitaxial films of yttrium iron garnet (Y 3 Fe 5 O 12 , YIG) is supported by potential applications in magnonic devices [1][2][3], exploiting the idea of data transfer via spin waves (SWs) [4]. Magnonic applications are based on nanostructures, where SW can propagate with reduced loss over distances up to millimeters.…”