Yttrium Iron Garnet Slab Research Articles

Giant enhancement of vacuum friction in spinning YIG nanospheres

Experimental observations of vacuum radiation and vacuum frictional torque are challenging due to their vanishingly small effects in practical systems. For example, a nanosphere rotating at 1GHz in free space slows down due to friction from vacuum fluctuations with a stopping time around the age of the Universe. Here, we show that a spinning yttrium iron garnet (YIG) nanosphere near aluminum or YIG slabs generates vacuum radiation with radiation power eight orders of magnitude larger than other metallic or dielectric spinning nanospheres. We achieve this giant enhancement by exploiting the large near-field magnetic local density of states in YIG systems, which occurs in the low-frequency GHz regime comparable to the rotation frequency. Furthermore, we propose a realistic experimental setup for observing the effects of this large vacuum radiation and frictional torque under experimentally accessible conditions.

Experimental realization of topologically protected unidirectional surface magnon polaritons on ceramic YIG ferrites

Topologically protected, unidirectional surface magnon polaritons (SMPs) guided along the interface between air and ferrimagnetic yttrium iron garnet slab structures, biased with an external static magnetic field in the Voigt configuration, are realized experimentally by measuring the S-parameters between two small loop magnetic dipole antennas that launch and receive the SMP. Transmission is compared in the two cases where an abrupt change in the form of a step is present and absent in the interface. We find that transmission of the SMP peaks near the same level in each case, a sign of its topological protection. In addition, the dependence of isolation on slab thickness is investigated for a specified antenna configuration.

Local heat emission due to unidirectional spin-wave heat conveyer effect observed by lock-in thermography

Lock-in thermography measurements were performed to reveal heat source distribution induced by the unidirectional spin-wave heat conveyer effect (USHCE) of magnetostatic surface spin waves. When the magnetostatic surface spin waves are excited in an yttrium iron garnet slab, the lock-in thermography images show spatially biased sharp and complicated heating patterns, indicating the importance of edge spin-wave dynamics for USHCE. The accessibility to the local heat emission properties allows us to clarify a capability of remote heating realized by USHCE; it can transfer energy for heating even through a macro-scale air gap between two magnetic materials owing to the long-range dipole–dipole coupling.

Nonreciprocal Isolating Bandpass Filter With Enhanced Isolation Using Metallized Ferrite

The nonreciprocal bandpass filter has been achieved by utilizing the nonreciprocity characteristics of the magnetostatic surface wave (MSSW) in planar ferrite slabs. In this article, the dispersion relation, impedance, and attenuation of MSSW between the pure and metallized ferrite slabs have been analyzed and compared. Theoretical analysis indicates that the ferrite slab metallized by a thin conductive layer would introduce significant attenuation on the metallized interface, which is MSSW propagating on the isolated direction, while MSSW on the other surface is barely affected. Therefore, nonreciprocal bandpass filter with enhanced isolation can be achieved with metallized ferrite slab. Simulated S-parameters show that a notch in the isolating direction can be obtained at the passing band of the transmitting direction. Experimental results show that the nonreciprocal filter with metallized yttrium iron garnet (YIG) slab (by depositing 100- $\mathbf {nm}$ copper film) exhibits more than 10-dB higher isolation than that with pure YIG slab, while the center frequency, insertion loss, and 3-dB bandwidth maintain almost the same. The center frequency of the filter with metallized YIG slab can be tuned from 7.26 to 8.38 GHz with insertion loss of less than 3 dB, and in-band isolation of more than 30 dB as the dc bias magnetic field is increased from 1.8 to 2.3 kOe. Besides, the nonreciprocal filter has ultra-wide out-band suppression since it utilizes the narrow frequency band of MSSW. The −10-dB out-band rejection exceeds 36 GHz in the upper band and 1 MHz in the lower band.

Spin‐thermoelectric voltage in longitudinal SSE elements incorporating LPE YIG films and polycrystalline YIG slabs with an ultrathin Pt layer

AbstractA spin‐thermoelectric (STE) voltage is generated when a temperature gradient ∇T is applied to an element having a thin Pt layer coated on a magnetic substance. In this study, yttrium iron garnet (YIG) ferrimagnetic films prepared by liquid phase epitaxy (LPE) were tested as magnetic insulators. In addition, polycrystalline YIG slabs were tested to compare the STE voltages of film and slab samples. In a Pt coating and YIG film bilayer structure made by an ultrathin Pt layer of 1‐4 nm thickness and an LPE film of approximately 10 µm thickness, a large STE voltage of 600 µV was observed at a probe distance of 5 mm with a temperature difference ∆T of 30 K. On the other hand, the STE voltage of a Pt layer and YIG slab bilayer structure was 340 µV, which is roughly half of that of the Pt/YIG‐film element. The cause of the large voltage observed experimentally for the longitudinal spin Seebeck effect element incorporating an LPE YIG film was discussed mainly from the viewpoint of the Pt layer resistivity and the effects of YIG specimen surface conditions on crystallinity and the magnetization process.

Tunable Bandpass Filter Using Partially Magnetized Ferrites With High Power Handling Capability

Low-loss tunable bandpass filters (BPFs) using partially magnetized ferrites is presented. A magnetic field tunable BPFs was designed based on partially magnetized yttrium iron garnet (YIG) operating at 6.17 GHz, which shows low insertion loss and a large frequency tunability of ~6% under a low bias field of 100 Oe. Power handling measurement on the tunable BPF with partially magnetized YIG slab showed an IP1dB of 11.5-18 dBm within the bias field of 0 to 100 Oe, and over 30 dBm in a saturated state.

A Novel Tunable Planar Isolator with Serrated Microstrip Structure

A novel type of tunable isolator was presented, which was based on a polycrystalline yttrium iron garnet (YIG) slab loaded on a planar periodic serrated microstrip transmission line that generated circular rotating magnetic field. The direction of circular polarization inside the YIG slab with a DC magnetic bias perpendicular to the transmission line was proved to be opposite, RHCP for forward and LHCP for backward transmission. The non-reciprocal ferromagnetic resonance absorption leads to over 19 dB isolation and <; 3.5 dB insertion loss at 13.5 GHz with 4 kOe bias magnetic field applied perpendicular to the feed line. Furthermore, the tunable resonant frequency of 4 ~ 13.5 GHz was obtained for the isolator with the tuning magnetic bias field 0.8 kOe ~ 4 kOe. The proposed serrated microstrip isolator prototype should have many applications in RF front and other microwave circuits.

Spin current injection by spin Seebeck and spin pumping effects in yttrium iron garnet/Pt structures

It is reported an investigation of pure spin current injection in Pt strips deposited on yttrium iron garnet (YIG) films by means of the spin pumping (SPE) and spin Seebeck (SSE) effects. Both effects were characterized by measuring the DC voltage created along the Pt strips by means of the inverse spin Hall effect (VISHE). SPE and SSE are simultaneously activated by exciting the ferromagnetic resonance (FMR) of the YIG film at the same time that a temperature gradient is created along the sample length. While the FMR signal is little affected by the temperature gradient, the voltage measured at the Pt strip placed at the lower temperature end exhibits a very challenging behavior. The voltage excited by the FMR uniform mode increases by six times as the temperature difference (ΔT) between the two ends of the YIG slab changes from 0 to 12 K. In contrast the VISHE generated by other magnetostatic spin-wave modes decreases to zero as ΔT varies from 0 to 12 K.

Low-Loss, Broadband and Tunable Negative Refractive Index Metamaterial

This paper report on a low-loss, broadband, and tunable negative refractive index metamaterial (NRIM) consisting of yttrium iron garnet (YIG) slabs and printed circuit boards (PCBs). The YIG slabs under an applied magnetic field provide a negative permeability and the PCBs provide a negative permittivity. The substrates of the PCBs decuple the interactions between the YIG slabs and wire array deposed on such substrates. The effective electromagnetic parameters of the NRIM and the conditions of exhibiting the negative refractive index character are analyzed theoretically. Then the negative transmission and negative refraction characters are investigated numerically and experimentally. The results indicate that the NRIM exhibits negative pass band within the X-band with a bandwidth of about 1 GHz and a peak transmission power of about - 2.5 dB. While changing the applied magnetic field from 2300 Oe to 2700 Oe, the measured pass band of NRIM shift from 8.42 GHz to 9.50 GHz with a 2.7 MHz/Oe step. The results open a sample way to fabricate the NRIM, further, the metamaterial cloak and absorber.

A microstrip tunable negative refractive index metamaterial and phase shifter

A tunable negative refractive index metamaterial and miniature phase shifter have been designed and fabricated in a microstrip configuration for applications in radio frequency integrated circuits. The metamaterial consists of plasmonic copper wires and yttrium iron garnet slabs having a low insertion loss of 5dB at the center of the transmission band. The yttrium iron garnet material enables the magnetic field tuning of the negative refractive index in a dynamic frequency band from 7.0to11.0GHz. The insertion phase can be tuned by 45° continuously by varying the bias field from 3.8to4.6kOe at 9.0GHz.

Magnetotunable left-handed material consisting of yttrium iron garnet slab and metallic wires

A magnetotunable left-handed material (LHM) consisting of yttrium iron garnet (YIG) slab and metallic wires has been demonstrated by experiments and simulations. The left-handed passband through the LHM can be dynamically and continuously tuned in a wide frequency region by an applied magnetic field. The tunability of the passband is attributed to that of the negative permeability induced by ferromagnetic resonance in the YIG slab. The authors proposed a convenient means to design tunable LHM based on the ferromagnetic materials as an alternative to tunable split ring resonators.

Ferrite-Coupled Line Circulator Simulations For Application at X-Band Frequency

We have designed and simulated a circulator circuit in which the magnetization aligns along the plane of an yttrium iron garnet (YIG) film. For an X-band frequency (8-12 GHz) circulator we have utilized a YIG slab (~200 mum thick) with saturation magnetization (4piMS ) and ferrimagnetic resonance (FMR) linewidth (DeltaH) of ~139.26 kA/m and 10 Oe, respectively. Broadband circulator operation was realized for frequencies above FMR, f=5 GHz. The applied FMR field was 79.58 kA/m. The Ansoft HFSS software suite was used to simulate the circulator response. The insertion loss S21 and the isolation S12 were calculated to be ~0.9 dB and ~-52 dB, respectively, with ~15% bandwidth at the center frequency of 10.1 GHz. We believe that this in-plane circulator design may enable high performance with significant volume and weight reduction

Role of Ferrites in Negative Index Metamaterials

Metamaterial composites consisting of copper wires and yttrium iron garnet (YIG) slabs have been theoretically studied using the transfer function matrix technique and predictions of electromagnetic scatterings have been compared well with experiments. An array of copper wires (without ferrite) showed plasma-like behavior in the calculation and was confirmed experimentally. The addition of a YIG slab demonstrated the effect of negative index. We believe that such a ferrite-wire metamaterial should provide low-loss and tunable negative index media (NIM) structures.

Characteristics of millimeter-wave radiation in a corrugated ferrite slab structure

The characteristics of millimeter-wave radiation in a corrugated ferrite slab supported by a grounded dielectric slab are investigated both theoretically and experimentally. Theoretical analysis is performed by the perturbation theory combined with multiple space scales for the transverse electric mode. A pair of amplitude transport equations are derived, and the characteristics of the leaky wave are explained in terms of the radiation angle and the radiation efficiency. Experiments were carried out using a layered structure composed of a corrugated polycrystalline yttrium iron garnet slab and a Teflon slab in the frequency range from 40 to 50 GHz. The experimental results are compared with the theory.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Magnetostatic Wave Propagation in a Finite YIG-Loaded Rectangular Waveguide

The propagation of magnetostatic waves (MSW) in a waveguide partially loaded with a low-loss ferrite slab is investigated theoretically. The most common low-loss ferrite material used for MSW propagation is epitaxial yttrium iron garnet (YIG). A YIG slab is placed inside and along the guide and not in contact with the sidewalls of the wavegnide. The dc magnetic field is assumed to be parallel to the YIG slab and perpendicular to the direction of propagation. Using the integral equation method, the dispersion relation is found to be an infinitely large determinant equal to zero. Proper truncation of this determinant and numerical analysis to find its roots are carried out in this work. It is seen that in order to obtain high values of group time delay, the YIG slab must be narrow and placed at the bottom of the guide. On the other hand, to maximize the device bandwidth, a narrow YIG slab positioned at the top inside surface of the waveguide is preferred. It is also noticed that there exists a tradeoff between the time delay and the device bandwidth and that maximization of one property leads to a poor value in the other. Thus, some design compromises should be made. It is also observed that the frequency range of operation of the device can be adjusted by an external magnetic bias field. This property of tuning the device to operate in any frequency range adds an extra dimension of flexibility to the operation and also to the design of these devices.

Bragg reflection of millimeter waves by a corrugated ferrite slab

Bragg reflection characteristics of millimeter waves from a corrugated ferrite slab are investigated theoretically and experimentally. Theoretical analysis is performed by using a singular boundary perturbation procedure. Experiments are carried out at millimeter wave frequency with a corrugated polycrystalline yttrium iron garnet slab. Typical results obtained are stop bandwidth of 600 MHz at a Bragg frequency of 46.7 GHz with a 2.5-dB insertion loss. The Bragg frequency is tunable over the range of 1.2 GHz by changing the applied dc magnetic field. Experimental results show satisfactory agreement with theoretical predictions.