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The magnon propagation length (MPL) is one of the crucial factors to govern spin transport in a magnetic material. Here, we determine MPL ($\xi$) in compensated ferrimagnetic Gd3Fe5O12 (GdIG) thin films at room temperature by investigating longitudinal spin Seebeck effect (LSSE) in Gd3Ga5O12 (GGG)/GdIG($t$)/Pt (5 nm) heterostructures with different thicknesses ($t$) of the GdIG film. All films possess in-plane (IP) magnetic easy axis, and the compensation temperature shifts down to lower temperature with decreasing GdIG thickness. At room temperature, the LSSE signal is rather constant with thickness between $t = 221$ and 89 nm, but drops significantly below $t = 50$ nm. By fitting the thickness dependence of the LSSE voltage to a modified atomistic spin model considering the influence of saturation magnetization, we obtain $\xi $ = 45 nm ± 8 nm for GdIG thin films at room temperature. The MPL of GdIG is much shorter than that of Y3Fe5O12 films ($\xi $ ~90–140 nm), but higher than that of Fe3O4 films ($\xi $ ~20 nm). The obtained value of $\xi $ explains the drop in the LSSE voltage in GdIG films when the film thickness is reduced below 50 nm, knowledge of which is also essential to the design of spincaloritronic devices based on GdIG films. [ABSTRACT FROM AUTHOR]

The electromagnetic (EM) properties of shielded gyromagnetic spheres are characterized with the aid of an electrodynamic model formulated for the transverse electric (TE) modes of an isotropic sphere, in a similar way as dielectric resonators are commonly analyzed. Broadband characteristics of geometric and energy filling factors are presented. A new measure of the magnetic loss tangent is introduced which is positive despite the intrinsic permeability of the gyromagnetic medium being negative, where existing definitions yield a non-physical negative value. The sample size dependence of those quantities is also assessed. The conclusions from the analysis are applied to investigate and de-embed ferromagnetic linewidth errors which can occur in broadband measurements of magnetic garnet spheres. Magnetic anisotropy fields and the gyromagnetic $g$ -factor are also estimated from the measurement data. Experiments were performed in a two-port subwavelength cavity, covering a frequency range of up to 28 GHz. Additionally, two-port rectangular resonant cavity linewidth measurements at a few modes have been conducted. Good agreement between the two methods is found if the systematic error is accounted for. [ABSTRACT FROM AUTHOR]

Direct epitaxial integration of magnetic layers with wide bandgap nitride semiconductors will enable spin-controlled transport and photonic phenomena, seeding ideas for functional spintronic devices. Using plasma-assisted molecular beam epitaxy (MBE) in a previously unexplored window, significantly improved ferrimagnetic Mn4N layers are successfully grown on GaN with ~1 nm surface roughness. Distinct from earlier reports, the Mn4N layers grown on GaN are found to be [001] oriented with 12-fold in-plane symmetry in the diffraction pattern. This unique epitaxial registry originates from three equivalent rotational domains. The ferrimagnetic magnetotransport properties of low growth temperature Mn4N layers on GaN are comparable to those reported on cubic substrates such as MgO. However, a sign-flip of the Hall resistance is discovered for Mn4N layers grown above 300 °C. [ABSTRACT FROM AUTHOR]

An advanced digital feedback algorithm providing defined waveform shapes of magnetic flux density (as well as induced voltage) is demonstrated. The algorithm is based on the iterative process predicting the exciting field waveform to be used in order to achieve the desired waveform of the voltage induced in the secondary winding along with the use of advanced hardware configuration utilizing appropriate exciting power amplifier (AMP) acting as a voltage-to-current converter. An approach based on the inverse function computation [inverse function digital feedback (IFDF)] applied to the response of the sample under test (SUT) to the initial exciting field waveform was used to estimate the exciting field that should be applied to magnetize the sample. SUT is usually made of ferromagnetic/ferrimagnetic material, thus constituting basically a nonlinear hysteretic system. Due to the nonlinearity and hysteresis, the iterations have to be repeated more times until the differences between actual and ideal waveforms fit into the required limits based on the chosen criteria, such as form factor (FF), total harmonic distortion (THD), and sample Pearson’s correlation coefficient (rxy). The effectiveness of the algorithm is subjected to testing on various magnetic materials in a wide range of frequencies and amplitudes of the exciting field/flux density in order to judge its robustness and stability as well as the number of iterations steps (or time) needed to obtain the satisfactory waveform shape. [ABSTRACT FROM AUTHOR]

Gold (50 nm)/bismuth ferrite (BFO) (100 nm) metal-semiconductor Schottky junction is fabricated using pulsed laser deposition (PLD) method on a Si substrate. BFO (BiFeO3) target for PLD deposition was made using BFO nanoparticles synthesized through sol-gel method. The forward- and reverse-bias current-voltage (I-V) characteristics of Au/BFO junction exhibit rectifier characteristics. The threshold voltage (Vγ) is 0.3 V which is in agreement with that of a conventional Schottky diode. I-V measurements were done with and without dc magnetic fields (H) to show the tuning of threshold voltage and forward-bias diode current. I-V characteristic shows distinct hysteresis behavior indicating hysteretic switching. Further, the fabricated diode was used as a half-wave rectifier. It has been demonstrated that the Au/BFO Schottky diode is a better high-frequency signal processing diode in comparison to a normal p-n junction silicon diode. Output waveforms were taken over a range of frequencies for both Au/BFO and Si diodes. An Si diode cannot rectify above 10 kHz, whereas Au/BFO junction diode can rectify even up to 1-MHz frequency. At high-frequency, Au/BFO diode exhibits “capacitor filtering effect,” resulting in higher dc voltages. [ABSTRACT FROM AUTHOR]

A method that allows the determination of magnetic permeability in magnetic bodies, as well as the ferromagnetic resonance (FMR) linewidth, by measuring only the quality factor and the resonant frequency of the perturbed microwave cavity at FMR is presented. The method is based on a set of equations derived for various types of magnetic media, including ferrites, single crystals, and polycrystalline materials. The evaluation of resonators containing magnetic medium is considered, and a detailed description of the spectrometer and the experimental procedure are presented. Independently measured yttrium iron garnet samples were used to validate the method. [ABSTRACT FROM PUBLISHER]

We investigated the anomalous Hall effect and longitudinal magnetoresistance in ferrimagnetic Co90Gd10 thin films with thicknesses from 5 to 35 nm and temperatures from 80 to 300 K. As the temperature increases from 80 to 300 K, the saturation magnetization of Co90Gd10 increases from 720 to 844 emu/cm3. However, the scaling law \sigma xy – \sigma xx^{n} with $n =2.3$ holds surprisingly well. Our results indicate that the scaling law usually reported in ferromagnetic materials remains valid for ferrimagnetic materials, which undoubtedly suggested the universality of the scaling law. [ABSTRACT FROM AUTHOR]

The aim of this paper is the analysis of the multipactor effect in a parallel-plate waveguide when a ferrite slab, transversally magnetized by a static magnetic field parallel to the waveguide walls, is present. Employing an in-house developed code, numerical simulations are performed to predict the multipactor radio frequency voltage threshold in such a ferrite-loaded waveguide. Variations of the ferrite magnetization field strength and the ferrite slab height are analyzed. Effective electron trajectories are also shown for a better understanding of the breakdown phenomenon, finding different multipactor regimes. [ABSTRACT FROM AUTHOR]

In this work, we report the synthesis, structure and magnetic properties of SrFe11T1O19 (T= \Ga,\Cr,\In,\Al) hexaferrite powders obtained by Pechini method. For all the samples, formation of the M-type structure was verified, together with a significant grain size coarsening, from 100 to 3000 nm. The magnetic properties include remarkable coercivity values of up to 590 kA/m, together with Curie temperatures within the range 652 K to 730 K across the compositional series. The coercivity variation was explained in terms of the evolution from single-domain magnetic particles to multidomain particles as a consequence of the significant grain growth. [ABSTRACT FROM PUBLISHER]

Millimeter wave (MMW) absorption measurements have been conducted on commercial samples of large (micrometer-sized) and small (nanometer-sized) particles of BaFe12O19 and SrFe12O19 using a quasi-optical MMW spectrometer and a series of backwards wave oscillators encompassing the 30–120 GHz range. Effective anisotropy of the particles calculated from the resonant absorption frequency indicates lower overall anisotropy in the nano-particles. Due to their high magnetocrystalline anisotropy, both BaFe12O19 and SrFe12O19 are expected to have spin resonances in the 45–55 GHz range. Several of the sampled BaFe12O19 powders did not have MMW absorptions, so they were further investigated by DC magnetization and x-ray diffraction to assess magnetic behavior and structure. The samples with absent MMW absorption contained primarily iron oxides, suggesting that MMW absorption could be used for quality control in hexaferrite powder manufacture. [ABSTRACT FROM AUTHOR]

The effects of deposition order on the magnetic properties of the NiFe/NiMn exchange couple were studied. The use of a thin underlayer, to enhance these properties, was also investigated for the deposition order NiMn/NiFe. We found that the use of such an underlayer was essential for the exchange field to be greater than the coercivity. We observed that the underlayer film thickness did not have a dramatic effect on the final exchange field obtained. X-ray diffraction studies did not reveal a strong correlation between film texture and exchange fields. The blocking temperature was also measured for the deposition order NiFe/NiMn. [ABSTRACT FROM PUBLISHER]