Yttrium Garnet Research Articles

Heat Capacity and Features of the Phonon Spectrum of Single Crystals of Solid Solutions of Yttrium–Lutetium Aluminum Garnets

The temperature dependences of the heat capacity were measured and the general patterns of the formation of the phonon spectrum of single crystals of solid solutions of yttrium-lutetium aluminum garnets Y3 – xLuxAl5O12 at 0 ≤ x ≤ 3 were investigated in the temperature range from 1.9 to 220 K. According to the data obtained at temperatures below 10 K, the Debye temperatures were calculated. The features of the phonon spectrum in the intermediate temperature range are interpreted as a superposition of optical modes for yttrium and lutetium garnets. It is shown that the low heat capacity values due to the contribution of acoustic phonons for Y2.25Lu0.75Al5O12 correlate with anomalies in the concentration dependences of the phonon transport, the absorption of acoustic waves, and the shape of the aluminum NMR line.

Propagation of spin waves in a lattice of laterally and vertically coupled YIG microwaveguides by changing the magnetization angle in linear and nonlinear modes

Purpose. Investigation of the joint manifestation of the effects of anisotropic signal propagation, coupling, and nonlinear power dependence of the medium parameters in a lattice of laterally and vertically coupled spin-wave (SW) microwaveguides. Consideration of the case of the influence of the rotation of the magnetization angle and the change of the lateral gap between microwaveguides located on the same substrate on the transverse profile of the spin-wave beam and the spatial localization of the SW amplitude. Methods. The method of micromagnetic modeling based on the numerical solution of the Landau–Lifshitz–Hilbert equation shows the possibility of controlling the direction of propagation of SW in an ensemble of laterally and vertically coupled iron yttrium garnet (YIG) microwaveguides by changing the magnetization angle. By the method of numerical integration of the system of coupled discrete nonlinear Schrodinger equations, the possibility of changing the transverse profile of the spin-wave beam by changing the level of the initial signal amplitude is shown. Results. The spatial distributions of the components of the dynamic magnetization of the SW excited in two microwaveguides located on the same substrate obtained in micromagnetic simulations indicate a change in the character of localization of the SW power in the output sections of the microwaveguides. At variation of the lattice magnetization angle, a shift of the threshold power value is observed, at which a characteristic curbing of the transverse width of the spin-wave beam in the nonlinear mode appears. Conclusion. When excitation of surface magnetostatic SW in a lattice of laterally and vertically coupled microwaveguides, a transformation of the transverse profile of the wave is observed at a deviation of the magnetization angle of the structure by 15º , which is manifested in the change of the SW length and its localization in each of the microwaveguides. The combined effects of dipole coupling, gyrotropy, and nonlinearity of the medium make it possible to control the value of the threshold power of the SW, at which the mode of diffractionless propagation of the spin-wave beam is realized in a single layer of the structure.

Analysis of cerium-substituted yttrium iron garnets by inductively coupled plasma atomic emission spectrometry with preliminary microwave decomposition

An analytical procedure for inductively coupled plasma atomic emission (ICP-AES) analysis of iron garnets of the composition Y3 – xCexFe5 – yGayO12, where x = 0.4 – 0.5 and y = 2.4 – 2.6 with preliminary microwave decomposition of the sample is described. The compositions of acid mixtures (HCl/HNO3), as well as modes of microwave heating (holding time and temperature), providing complete dissolution of the samples are proposed. In addition to optimized sample preparation, conditions for ICP-AES analysis of cerium-doped yttrium iron garnets were studied. The effect of matrix components (Y, Ce, Fe, Ga) on the determination of doping elements was revealed and studied. The operating parameters of the spectrometer (ICP power and nebulizer flow rate) have been substantiated, which make it possible to reduce the matrix effect of Fe, Ga, Y, Ce on the elements Na, Mg, Al, Si, P, K, Ca, Sc, Cr, Mn, Co, Ni, Cu, Zn, Se, Cd, Sn, Te, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Pb in iron yttrium garnets by the ICP-AES. ICP-AES measurements were performed in the axial and radial mode for trace elements and in the radial mode for matrix elements. The limits of quantification (LOQs) of most elements ranged within n × 10–5 – n × 10–4 wt.%. The accuracy is confirmed by the spike recovery test. The relative standard deviation is in the range of 1 – 5% depending on the selected plasma view mode and the analyzed analytes. The developed method makes it possible to determine macro- and microcomponents in yttrium iron garnets in a wide range of concentrations with a high accuracy.

Excitation of exchange spin waves in the transition layer of the two-layer ferrite-ferrite structure

The possibility of intense excitation of exchange spin waves in a tangentially magnetized two-layer epitaxial film of iron yttrium garnet is demonstrated. The waves are excited in a thin transition layer at the interface between the ferrite layers, propagate into the doped layer with reduced magnetization, and reflect from its opposite surface. In continuous excitation mode, they can be observed as a series of spin wave resonance peaks. Mathematical processing of the measured frequencies of resonance peaks allows for the calculation of the magnetization profile of the doped layer and the modeling of the excitation and propagation processes of exchange spin waves. The proposed methodology of mathematical processing can be applied for non-destructive control of the layered structure of epitaxial ferrite structures.

Comparative Evaluation of Fibrin Network Formation after Root Conditioning using Erbium, Chromium-Doped Yttrium Scandium Gallium and Garnet Laser, Ethylene-Diamine-Tetra-Acetic Acid, and Tetracycline on Dentin: A Scanning Electron Microscopic Study.

Regeneration of periodontal tissues depend on the adhesion and development of fibrin clots to the root surface. Demineralization of the root surface ensures removal of smear layer uncovering dentin tubules and collagen matrix. Root conditioning agents were introduced to remove the smear layer and enhance the adhesion of blood components. The aim of the study was to determine the effect of erbium, chromium-doped yttrium, scandium, gallium and garnet (Er, Cr: YSGG) laser on smear layer removal (SLR) and fibrin network formation when compared to tetracycline, and ethylene-diamine-tetra-acetic acid (EDTA) for periodontal regeneration. The study was conducted at Amrita school of dentistry and the study design involves in vitro comparative study. Forty dentinal sections were prepared from freshly extracted teeth that were periodontally affected. The samples were divided into four groups: Scaling and root planing (SRP), tetracycline, EDTA, and Er, Cr: YSGG laser. The samples were assessed using a scanning electron microscope and photomicrographs were taken and analyzed for removal of smear layer, blood component adhesion (BCA), and fibrin network formation. Analysis of variance test and Kruskal-Wallis test with P < 0.05 considered to be statistically significant. There was a significant difference between Er, Cr: YSGG laser, tetracycline hydrochloride, and EDTA categories when compared with SRP categories. There was no significant difference between Er, Cr: YSGG laser, tetracycline, and EDTA according to SLR scoring and BCA scoring. It can be concluded that Er, Cr: YSGG laser-treated samples presented complete elimination of smear layer, formation of fibrin network, and BCA along with desensitizing effect for a better reduction in dentin hypersensitivity.

Excitation of exchange spin waves in a two-layer ferrite-ferrite structure

The possibility of intense radiation of short-wave exchange spin waves excited in a thin transition layer at the internal boundary of a bilayer ferrite-ferrite structure is shown. Modelling of radiation processes has been exemplified by a tangentially magnetized bilayer film of ferric-yttrium garnet. It was found that the radiation of exchange spin waves has one-way character. The waves were radiated into the layer with decreased magnetization. Their group velocities were an order of magnitude lower than sound velocity in iron-yttrium garnet. Obtained results may be useful for creation of miniature controllable delay line on exchange spin waves. Keywords: spin waves, ferrite, iron yttrium garnet, delay line.

Spin wave computing using pre-recorded magnetization patterns

We propose a novel type of spin wave computing device, based on a bilayer structure that includes a “bias layer” made from a hard magnetic material and a “propagation layer” made from a magnetic material with low damping, for example, yttrium garnet or permalloy. The bias layer maintains a stable pre-recorded magnetization pattern, which generates a bias field with a desired spatial dependence, which in turn sets the equilibrium magnetization inside the propagation layer. When an external source applies an RF field to the propagation layer, excited spin waves scatter on the magnetization's inhomogeneities resulting in complex interference behavior. This scattering interference can be utilized to perform a variety of mathematical operations including Vector-Matrix multiplication. The spatial dependence of such magnetization patterns can be estimated via perturbation theory.

Investigation of the structural and magnetic properties of Y2.8Ca0.2Fe5-Al M O12 (M = Mn and Cr, x = y + z)

• The sol–gel method was used to prepare Y 2.8 Ca 0.2 Fe 5-x Al y M z O 12 (M = Mn and Cr, x = y + z) ferrites at the temperature of 1300 K. • XRD, SEM, EDX and XPS were used to characterize the structure of samples. • B-H magnetic characteristic analyzer and VSM are used to characterize magnetic properties of different ions doped in YIG . • When the Al ions content amount achieves 0.3 and Cr ions content amount achieves 0.4, the magnetic properties of the sample are the best. The structural and magnetic properties of yttrium iron garnet Y 2.8 Ca 0.2 Fe 5- x Al y M z O 12 (M = Mn and Cr, x = y + z ) samples by the sol–gel method were investigated in this paper. Different ion doping can change the structure of the samples and improve the saturation magnetization and permeability of YIG. The lattice constant of all samples was found to vary slightly as the Al, Mn, and Cr ions were doped. Al, Mn, and Cr ions have different effects on the change in permeability and saturation magnetization and are explained in detail. With increasing ion doping, the Curie temperature (T c ) transition point decreased. In this work, magnetic permeability achieved the maximum value of 174.6H/m. The power loss reached a minimum at an Al ion concentration of 0.3 and a Cr ion concentration of 0.4. Cr ions tend to occupy the (a) site first and then occupy the (d) site, and the superexchange interaction between the (a) and (d) sites increases. Therefore, the maximum permeability is achieved at an ion concentration of 0.4. Yttrium garnet can be used as a circulator to keep the signal flowing in one direction, and after broadening the application field of yttrium, garnet can be more widely used in 5G technology.

Short-Term Efficacy of Er:YAG Laser and Nd:YAG Laser Combined Therapy on Periodontitis.

Objective: The objective of this research is to assess the short-term efficacy of combined erbium-doped: yttrium aluminum and garnet (Er:YAG) and neodymium-doped: yttrium aluminum garnet (Nd:YAG) lasers for the nonsurgical treatment of periodontitis, providing a reliable basis for whether this clinical treatment can be applied in clinical practice. Materials and methods: Thirty patients with periodontitis are chosen for this study. A split-mouth design was used; the left and right quadrants of the oral cavity are randomly assigned to one treatment: combined Er:YAG laser and Nd:YAG laser treatment (laser group) or scaling and root planing (SRP) group. Data on probing depth, clinical attachment level, bleeding index, and subgingival plaque and gingival crevicular fluid samples are collected in the basement, for 1 and 3 months. The levels of red complexes in subgingival plaque and cytokines in gingival sulcus fluid were measured by real-time polymerase chain reaction and enzyme-linked immunosorbent assay. Results: At 1 and 3 months of follow-up, all clinical parameters in the two groups are significantly improved; there is a statistically remarkable difference between the laser group and SRP group (p < 0.001). Matrix metalloproteinase 8 levels in the laser group are notably lower than those in the SRP group 3 months after treatment (p < 0.001). At any point in time, the levels of red complexes in the laser group showed no additional advantage over those in the SRP group (p > 0.05). Conclusions: Er:YAG laser and Nd:YAG laser combined therapy on periodontitis have advantages in controlling periodontal inflammation and improving clinical symptoms.

Application of Ion‐Doped Y3Fe5O12 Nanoparticles for Self‐Controlled Magnetic Hyperthermia

Herein, doped yttrium garnet (YIG) nanoparticles (NPs) ( Al, Ga, Sc are nonmagnetic ions) are studied, appropriate for self‐controlled magnetic hyperthermia (SCMH) for in vivo and in vitro applications. A microscopic model (modified Heisenberg Hamiltonian) and the Green's function technique are used to investigate the temperature, doping, and size dependence of magnetic phase transition, saturation magnetization, the coercivity, and the specific absorption rate coefficient to fulfill the conditions for magnetic hyperthermia. A set of mixed yttrium garnet magnetic NPs is found, which are suitable for applications in medicine for cancer therapy. There are two Sc‐doped YIG NPs which are the best candidates for SCMH with x = 1.08, d = 27.5 nm, and = 13.52 as well as x = 1.10, d = 29.7 nm, and = 15.44 for which the conditions for biocompatibility and maximization of are fulfilled simultaneously. Moreover, also Al‐ and Ga‐doped YIG NPs are found that can be applied for magnetic hyperthermia but with smaller effectivity.

Spin wave propagation in a YIG/FeRh composite structure as a system of coupled microwaveguides

In this paper present that it is possible to control the characteristics of spin waves (SW) in a system of lateral magnetic waveguides made of iron yttrium garnet (YIG) by changing the characteristics of the antiferromagnetic iron-rhodium (FeRh) layer located above these waveguides. In particular it is shown that by changing the geometric parameters and magnetization of the FeRh layer one can control the amplitude and phase of SW propagating in lateral microwaveguides. The modes under which dips appear on the transmittance amplitude-frequency response (AFR) due to redistribution of the SW power are revealed, and their location can be controlled by changing the properties of the FeRh layer. The results obtained can be used to create microwave demultiplexers and taps based on the proposed structure. Keywords: spin waves, antiferromagnetic, magnonics, lateral structures

Распространение спиновых волн в композитной структуре YIG/FeRh в виде системы связанных микроволноводов

In this paper present that it is possible to control the characteristics of spin waves (SW) in a system of lateral magnetic waveguides made of iron yttrium garnet (YIG) by changing the characteristics of the antiferromagnetic iron-rhodium (FeRh) layer located above these waveguides. In particular it is shown that by changing the geometric parameters and magnetization of the FeRh layer one can control the amplitude and phase of SW propagating in lateral microwaveguides. The modes under which dips appear on the transmittance amplitude-frequency response (AFR) due to redistribution of the SW power are revealed, and their location can be controlled by changing the properties of the FeRh layer. The results obtained can be used to create microwave demultiplexers and taps based on the proposed structure.

Spin-wave resonances in a diffusion-sensitive epitaxial film YIG

It is shown that in a tangentially magnetized film of iron yttrium garnet exist two types of resonances --- a homogeneous ferrimagnetic resonance in the region of the film's homogeneous magnetization (outside the diffusion layer), and inhomogeneous spin-wave resonance within the thickness of the diffusion layer. A method of calculating the magnetization distribution over the film thickness using measured frequencies of the spin-wave and ferrimagnetic resonances. The method of mathematical modeling has established that the magnetic inhomogeneity of the transition layer layer introduces significant distortions of the oscillation epure at the frequency of the spin-wave resonance, and the nature of the distortions significantly depends on the magnitude of the magnetizing field. The results of the conducted can be useful for nondestructive control of the layered structure of YIG epitaxial films. Keywords: yttrium iron garnet epitaxial films, exchange spin waves, spinwave electronics, magnonics.

Спин-волновые резонансы в диффузионном слое эпитаксиальной пленки ЖИГ

It is shown that in a tangentially magnetized film of iron yttrium garnet exist two types of resonances - a homogeneous ferrimagnetic resonance in the region of the film's homogeneous magnetization (outside the diffusion layer), and inhomogeneous spin-wave resonance within the thickness of the diffusion layer. A method of calculating the magnetization distribution over the film thickness using measured frequencies of the spin-wave and ferrimagnetic resonances. The method of mathematical modeling has established that the magnetic inhomogeneity of the transition layer layer introduces significant distortions of the oscillation epure at the frequency of the spin-wave resonance, and the nature of the distortions significantly depends on the magnitude of the magnetizing field. The results of the conducted can be useful for nondestructive control of the layered structure of YIG epitaxial films.

Calorimetry of DyxY3−xAl5O12 garnet solid solutions in magnetic field

We report the caloric and magnetocaloric properties of the DyxY3−xAl5O12 garnet single crystals (x = 0, 0.15, 0.5, 1, 1.5, 2.25, 3) studied within a large temperature range at magnetic fields up to 70 kOe. Heat capacity at zero field revealed that the Schottky anomalies ascribed to magnetic splitting the ground Kramers doublet of Dy3+ ions induced by neighbor ions. The low-temperature heat capacity was fitted by a sum of the Debye and Schottky contributions. The antiferromagnetic transition above 1.9 K was observed only for the pure dysprosium aluminum garnet. The shifts of the Schottky anomalies in magnetic fields agreed with strong anisotropy of the g-factor of Dy3+ ions in the c-sites. The Dy3+ ions in the non-stoichiometric positions caused additional weak anomalies in the heat capacity. The heat capacity for the garnet with x = 1 demonstrated strong clustering for this particular composition. The results obtained showed that the measurements of the heat capacity in magnetic field can be used to get information on substitutional disorder and non-stoichiometry in solid solutions. The magnetic entropy was evaluated for the dysprosium-comprising garnets. The pronounced magnitude of the magnetic entropy owing to the Schottky anomalies shows the applicability of the mixed dysprosium yttrium garnets to adiabatic refrigerators.

Features of the Coupled Nuclear–Electron Spin Precession in the Bose–Einstein Condensate of Magnons

The experimental detection of the Bose-Einstein condensate of magnons in coupled nuclear-electron spin precession in antiferromagnets brings the prospect of its use for magnonics and computer calculations. In particular, an attractive feature of such systems is a relatively large spin coherence time compared to traditional iron yttrium garnet samples. However, the observed Bose-Einstein condensation of magnons contradicts the Suhl-Nakamura model and the Bloch equations, which are usually used for these systems. The results of a direct experiment in antiferromagnetic MnCO3 performed in this work indicate that the Suhl-Nakamura model and the Bloch equations cannot adequately describe the coupled nuclear-electron spin motion at large levels of magnon excitation.

Electromagnetic Sound Excitation and the Optoacoustic Effect in Magnetostrictive Materials

The effect a magnetic field has on the parameters of ultrasonic vibrations during laser excitation in magnetostrictive materials is studied. Dimensional effects and quasi-resonant dependence of the intensity of the acoustic response on the magnetic field strength are observed in films of iron–yttrium garnet. The effect domains and domain boundaries in manganese–zinc spinel plates and polycrystalline nickel films have on the characteristics of an acoustic response during laser sound excitation in the presence of a magnetic field is established. The effect the strength of the magnetic field has on the spectrum of acoustic signals in the investigated materials is examined.

Propagation of a Surface Magnetoelastic Wave in a Ferromagnet Near the Orientation Phase Transition

The frequency dependences of the group velocity and the damping of a magnetoelastic surface wave have been studied at various values of an external magnetic field and various angles of propagation. The group velocity bursts are observed at frequencies, at which peaks of surface wave damping take place. The behavior of a surface magnetoelastic wave is also studied near the orientation phase transition. In the phase transition point, the group velocity is changed by 1%. The dependences of the damping along the surface at various angles of propagation indicate the nonreciprocal wave nature. In this work, all the dependences have been obtained using computer calculations and the ferromagnet parameters are taken to be typical for iron–yttrium garnet.

Rheological properties of Y3Al5O12 powder obtained by preceramic organoyttroxanealumoxanes

Submicron powder Y3Al5O12 (YAG) aluminium yttrium garnet was synthesized from an Al-Y-ceramic-forming precursor, according to the method developed in the State Research Institute for Chemistry and Technology of Organoelement Compounds (SRICTO). The advantage of the method is the possibility of obtaining close to the stoichiometric phase and obtaining high purity nanopowder. In this work, we studied the effect of the pyrolysis temperature of the polymer (700°, 800° and 900°C) and grinding time on the rheological properties of the powder. It was shown that after pyrolysis at 700° and 800°C, the powder has an amorphous structure, the ultimate strain, in this case, being 6.1 and 8.1% of the initial size. The compressibility modulus decreases with increasing temperature from 34.5 to 19.4 MPa. Due to the formation of YAG crystals after pyrolysis at 900°C, the compressibility of the powder increases and the compacts become denser.

Laser-induced spin dynamics in the iron-yttrium garnet film doped with Si ions

A continuous increase in the volume of stored and processed data leads to stricter requirements for storage media. The most common information storage technology is currently based on magnetic materials, where information in the form of 0 and 1 is associated with the local direction of magnetization, determined by the external magnetic field created by the recording device. It is known that this approach has fundamental limitations on the recording speed which is almost achieved. The requirements for energy efficiency of storage media are also being made stricter. These circumstances lead to the development of alternative approaches to recording information. One of these approaches has been demonstrated in the field of ultrafast opto-magnetism, which has been booming over the past 20 years. It consists in recording information with short optical pulses without the application of an external magnetic field. However, it requires fundamental studies of physical processes, as well as materials, in which magnetization can be controlled by short optical pulses. In this paper, we consider the spin dynamics in a magnetic dielectric: a film of iron - yttrium garnet doped with silicon. The studies were carried out using the pump – probe technique over a time range of up to 800 ns. The spot size was 30 μm, the optical pulse duration was 35 fs, and the pump fluence was about 50 mJ/cm 2 . It is shown that a change in the magnetocrystalline anisotropy constants due to the action of a pump pulse on the structure causes a long-decaying magnetization precession with a period of about 200 ps. The dependences of the amplitude, phase, and decay of the precession on the magnitude of the external magnetic field in the range up to 1.84 kOe were obtained and analyzed. The studied processes can be considered on the basis of the Landau-Lifshitz-Gilbert model, and be of interest for the optical switching of magnetization, as well as the creation of various spintronic devices. It is shown that films of iron-yttrium garnet doped with silicon are a promising material for magnetic information carriers based on ultrafast opto-magnetism.