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We report broadband magnetic resonance in polycrystalline Sr 2 FeMoO 6 measured over the wide temperature ( T = 10–370 K) and frequency ( f = 2–18 GHz) ranges. Sr 2 FeMoO 6 was synthesized by the sol–gel method and found to be ferromagnetic below T C = 325 K. A coplanar waveguide-based broadband spectrometer was used to record the broadband electron spin resonance (ESR) both in frequency sweep and field sweep modes. From the frequency sweep mode at fixed dc magnetic fields, we obtain the spectroscopic splitting factor g ∼ 2.02 for T ≥ T C K, which confirms the 3+ ionic state of Fe in the material. The effective g value was found to decrease monotonically with decreasing temperature in the ferromagnetic regime. Resonance frequency decreases and the line width of the spectra increases as the temperature decreases below T C . At room temperature (RT) and above, the line width (Δ H ) of the ESR signal increases linearly with frequency, giving Gilbert damping constant α ∼0.032 ± 0.005 at RT. However, at lower temperatures, a minimum emerges in the Δ H vs frequency curve, and the minimum shifts to a higher frequency with decreasing temperature, confining the linear frequency regime to a narrow-frequency regime. Additional inhomogeneous broadening and low-field-loss terms are needed to describe the line width in the entire frequency range.

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.

We report the electrical detection of multiple ferromagnetic (FM) resonance modes in multilayers of Pt/Fe20Ni80/Ru/Fe20Ni80 using microwave spin pumping and the inverse spin Hall effect (ISHE) as a function of Ru layer thickness tRu. The electrically detected voltage signals were analyzed for the anti-parallel magnetization state as well as the “spin-flop” magnetization state of the two Fe20Ni80 layers. When the two FM layers are antiferromagnetically (AFM) coupled (tRu = 1 nm), both the optic and acoustic modes were observed. The amplitude of the acoustic mode voltage signals obtained increases with frequency. However, when the two magnetic layers are ferromagnetically coupled (tRu = 1.4 nm), only acoustic mode was observed whose voltage signals decreases as frequency increases. We demonstrate the tunability of the sign of the ISHE voltage in the AFM coupled system by controlling the polarization of the spin currents.