Abstract
Rare-earth iron garnet thin films with perpendicular magnetic anisotropy (PMA) have recently attracted a great deal of attention for spintronics applications. Bismuth substituted iron garnets are particularly popular among these various films because Bi3+ with a larger ion radius can adjust the lattice constant, strain state, and PMA of the films. In this paper, Tm2BiFe5O12 (TmBiIG) and Y2BiFe5O12 (YBiIG) garnet films with a series of thicknesses are prepared by radio frequency magnetron sputtering, and these films exhibit robust PMA. The microstructural properties, magnetic properties, and the anomalous Hall effect of these two kinds of films are discussed in detail. Due to their larger magnetostriction coefficient and proper tensile strain, TmBiIG films exhibit better PMA than YBiIG films, which have lower damping. As the thickness of TmBiIG and YBiIG films increases, the PMA becomes weaker, and the 40 nm YBiIG turns back to in-plane easy magnetization, but PMA is still obvious for the 64 nm TmBiIG. The ferromagnetic resonance linewidth of the 32 nm TmBiIG film is 249.08 Oe @ 13 GHz, and the damping factor is 1.49 × 10−2, which is close to that of Tm3Fe5O12. YBiIG films have better damping characteristics than TmBiIG films; however, the value is larger than that of yttrium iron garnet because of surface roughness and defects caused by larger lattice mismatch. In addition, on account of fewer defects and smaller surface roughness, the Hall voltage and Hall resistivity in TmBiIG/Pt heterostructures are larger than in YBiIG/Pt.
Highlights
Rare-earth iron garnet (RIG) films, especially yttrium iron garnet (Y3Fe5O12, YIG) films, have played a significant role in microwave devices1,2 and magneto-optical devices3,4 because of the narrow ferromagnetic resonance (FMR) linewidth and large specific Faraday rotation angle
The XRD spectra of these films are obtained by scanning the ω/2θ of the (444) diffraction peaks, the intensity spectra of TmBiIG films are shown in Fig. 1(a), while that of YBiIG is shown in our past paper
The highresolution transmission electron microscopy (TEM) measurement has proved that these films were mono-crystalline
Summary
Rare-earth iron garnet (RIG) films, especially yttrium iron garnet (Y3Fe5O12, YIG) films, have played a significant role in microwave devices and magneto-optical devices because of the narrow ferromagnetic resonance (FMR) linewidth and large specific Faraday rotation angle. Kajiwara and co-workers successfully demonstrated spin pumping and spintransfer-torque in a YIG/Pt ferromagnetic insulator/heavy metal (FMI/HM) system.5 This provoked intensive studies of magnonics and spintronics, and a lot of research had focused on FMIs by the spin wave and spin current in FMI/HM heterostructures.. The (111) magnetostriction coefficients of most RIG films are negative, so tensile strain is helpful to PMA and the lattice constant of films is expected to be smaller than that of substrates. Quindeau and co-workers found scitation.org/journal/adv that Tm3Fe5O12 (TmIG) films can have robust PMA, which was mainly contributed by stress-induced anisotropy influenced by large magnetostriction coefficients. Tang and co-workers further enlarged stress-induced anisotropy by adopting a substituted gadolinium gallium garnet (SGGG) with a larger lattice constant as the substrate of TmIG.. Bi3+ occupies the dodecahedral position, which has a significant effect on the growth-induced anisotropy of films grown by LPE.
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