Magnetoimpedance of Epitaxial Y₃Fe₅O₁₂ (001) Thin Film in Low-Frequency Regime

Abstract

The atomically flat interface of the Y3Fe5O12 (YIG) thin film and the Gd3Ga5O12 (GGG) substrate plays a vital role in obtaining the magnetization dynamics of YIG below and above the anisotropy field. Here, magnetoimpedance (MI) is used to investigate the magnetization dynamics in fully epitaxial 45 nm YIG thin films grown on the GGG (001) substrates using a copper strip coil in the MHz–GHz frequency region. The resistance (R) and reactance (X), which are components of impedance (Z), allow us to probe the absorptive and dispersive components of the dynamic permeability, whereas a conventional spectrometer only measures the field derivative of the power absorbed. The distinct excitation modes arising from the resonance in the uniform and dragged magnetization states of YIG are respectively observed above and below the anisotropy field. The magnetodynamics clearly shows the visible dichotomy between two resonant fields below and above the anisotropy field and its motion as a function of the direction of the applied magnetic field. A low value of a damping factor of ∼4.7 – 6.1 × 10–4 is estimated for uniform excitation mode with an anisotropy field of 65 ± 2 Oe. Investigation of below and above anisotropy field-dependent magnetodynamics in the low-frequency mode can be useful in designing the YIG-based resonators, oscillators, filters, and magnonic devices.

Challenges and Applications to Operando and In Situ TEM Imaging and Spectroscopic Capabilities in a Cryogenic Temperature Range

“…The monocrystalline epitaxial ultralow-damping 10-μm-thick Y 3 Fe 5 O 12 films were grown on gallium gadolinium garnet (GGG) substrates using the liquid-phase epitaxy (LPE) technique , and covered by a 5.5-nm-thick Pt layer and a 200-nm-thick Al 2 O 3 dielectric layer (Figure a). The TEM was operated under a magnetic-field-free condition where the objective lens was switched off (Lorentz mode) …”

“…The operando studies were conducted on Y 3 Fe 5 O 12 lamella (1) by applying the magnetic field near the sample which was generated by passing the current through the objective lens, (2) by applying a pulsed current though the Pt layer, and (3) by changing the temperature of the sample. The coercive field for the Y 3 Fe 5 O 12 thin films is very small, thus the domain walls are expected to move easily (in-plane coercive field H s < 0.5 mT). Figure e­(i–v) shows the switching between two pinning sites by varying the applied magnetic field.…”

Directional Field-Dependence of Magnetoimpedance Effect on Integrated YIG/Pt-Stripline System

“…The magnetization dynamics in YIG films have been extensively probed through broadband ferromagnetic resonance in recent years; but the link between FMI materials and MI experiments remained elusive until recently [28][29][30][31]. With this spirit, connecting YIG and MI, Kang and coworkers [28], for instance, have addressed the dynamics in YIG spheres and a single-crystalline YIG film deposited by using liquid phase epitaxy.…”

“…The authors have disclosed very interesting results by employing a vector network analyzer (VNA) to perform MI measurements in a wide range of frequencies, with MI ratio values of around 256% and MI sensitivity of ∼8.8%/Oe for such systems. Next, Madwal and colleagues [29] have investigated a sputtered YIG single-layer thin film with a thickness of 45 nm. In this case, the magnetoimpedance experiments have been performed using the inductive method, in which a signal coil is wound around the film and surprisingly, despite the reduced dimension of the film, the FMR effect is found even at the low-frequency regime, from 0.5 up to 2.0 GHz.…”

Operando and in situ in a TEM imaging in a cryogenic temperature range

“…The propagation of magnetic domain walls in YIG, a magnetic insulator, is also studied by varying the temperature (from ~120 K to ~400 K), external magnetic field and electric current [6]. We use Lorentz TEM conditions (magnetic field-free conditions at the sample location) to image the displacement of domain walls in YIG crystal, first under different applied magnetic fields and then by applying different current densities in the adjacent metallic layer.…”