Single Yttrium Iron Garnet Research Articles

Sub-Poissonian statistics and squeezing of magnons due to the Kerr effect in a hybrid coupled cavity–magnon system

We investigate theoretically the quantum dynamics and statistics of magnons in a cavity–magnon system, where the magnons in a single yttrium iron garnet (YIG) sphere are coupled to microwave cavity photons. Under the rotating wave approximation, the Hamiltonian of the system is solved analytically. By using the coherent magnon state representation, we show that the magnon Kerr nonlinearity, which originates in the magnetocrystalline anisotropy in the YIG sample, could yield a periodic sub-Poissonian distribution and quadrature squeezing effects in the magnons. The generation and manipulation of these nonclassical quantum statistical properties of the magnons can be controlled by scaling the size of the YIG sample.

Brillouin light scattering study of transverse mode coupling in confined yttrium iron garnet/barium strontium titanate multiferroic

Using the space-resolved Brillouin light scattering spectroscopy we study the transformation of dynamic magnetization patterns in a bilayer multiferroic structure. We show that in the comparison with a single yttrium iron garnet (YIG) film magnetization distribution is transformed in the bilayer structure due to the coupling of waves propagating both in an YIG film (magnetic layer) and in a barium strontium titanate slab (ferroelectric layer). We present a simple electrodynamic model using the numerical finite element method to show the transformation of eigenmode spectrum of confined multiferroic. In particular, we demonstrate that the control over the dynamic magnetization and the transformation of spatial profiles of transverse modes in magnetic film of the bilayer structure can be performed by the tuning of the wavevectors of transverse modes. The studied confined multiferroic stripe can be utilized for fabrication of integrated dual tunable functional devices for magnonic applications.

Study of the magnetic disaccommodation in La doped YIG

The relaxation of the initial magnetic permeability of La doped yttrium iron garnet (YIG) samples with nominal composition Y3-xLaxFe5O12 (0< x <0.6) is analysed in this work. The results show a very different behaviour depending on the sintering atmosphere used for the fabrication of the samples. Concretely, for the samples sintered in air, it just have been detected the usual relaxation peak found in YIG at 130 K. However, a new relaxation peak appears around room temperature for the samples sintered in CO2 atmos- phere when the La content is at least of 0.3. These results have been interpreted in terms of the formation of a secondary perovskite phase when the La solubility limit is reached. It is well known that Yttrium Iron Garnet (YIG) is a key material for the development of microwave devices due to its electrical and magnetic properties and the possibility of introducing a wide range of dopants for tailoring its properties. It is very usual the substitution of iron by metallic cations in tetrahe- dral or octahedral sites of the lattice (1-3). However, the substitution of part of yttrium ions in dodecahe- dral sites with a rare earth element has been also studied so far (4, 5), showing that the total substitution of Y by lighter 4f rare earth elements La, Ce, Pr and Nd is not possible, and that, above the solubility limit, a secondary perovskite phase forms together with the magnetic garnet. In this sense, it is essential to determine the solubility limit of each extrinsic cation in order to assure that single YIG phase is ob- tained. Recently, our group has shown (6) that the magnetic disaccommodation technique is a powerful tool to analyse the garnet-perovskite transition in rare earth element doped YIG. This technique consists in the time variation of the mobility of domain walls after a magnetic shock, and is shown by a temporal evolution of the magnetic permeability after a demagnetization stage. This kind of phenomena, which is strongly temperature-dependent, is undesirable from the technical point of view, as it represents an im- portant source of magnetic losses in these materials, but it is very useful for basic research because such studies yield information about lattice symmetry and dynamics. Its origin has been attributed to either the rearrangement or the diffusion of anisotropic point defects, such as lattice vacancies and interstitials, within the Bloch walls. In this work we have studied the effect of La doping on the magnetic disaccom- modation of YIG samples fabricated under different sintering atmospheres.

Magnetic disaccommodation in single yttrium iron garnet crystal

Measurements of magnetic disaccommodation in single yttrium iron garnet (YIG) crystals are presented. Two peaks of 0.2%–0.3% are observed in the isochronal spectrum around 130 and 250 K. Comparison of our results with those on polycrystalline YIG samples and with similar data on illuminated and gamma ray irradiated single YIG crystal samples is provided.