Garnet Epilayers Research Articles

Study of Bi-substituted iron garnet epilayers by means of channeling

Magnetic films of bismuth substituted iron garnets have been investigated using He ion channeling. Rutherford backscattering and ion induced X-ray emission measurements have been made as a function of the thickness of the garnet epilayers. The lattice sites of bismuth and lead could be determined.

Compositional inhomogeneities along the growth direction of substituted yttrium iron garnet epilayers

Secondary ion mass spectrometric analyses calibrated by electron microprobe analyses reveal compositional inhomogeneities along the growth direction (thickness) of substituted yttrium iron garnet epilayers. Specially exaggerated growth conditions are induced by altering the substrate rotation rate during growth at high supercooling. These conditions cause changes of effective distribution coefficients with time.

Broadened low-field modes in thick yttrium iron garnet epilayers

Damped surface modes in thick YIG epilayers which appear at fields below the Damon-Eshbach limit in microwave spectra with the dc magnetic field parallel to the surface, have been investigated. The introduction of a surface anisotropy term in the boundary conditions of the propagation equations qualitatively accounts for these low-field modes.

Microwave losses induced by tetravalent iron in divalent ion substituted YIG epilayers

Microwave losses have been studied in two series of divalent cation-substituted yttrium iron garnet epilayers, Ca:YIG and Mg:YIG. Since CaO dissolves completely while MgO dissolves only partially in the fluxed melt, the magnetic losses caused by the Fe4+ions induced in the garnet lattice reach quite different magnitudes. Using microwave resonance and film etching, the concentration profiles of several Ca:YIG films have been studied. The effective gyromagnetic ratio of Ca:YIG films suggests that the Fe4+ion is located on the tetrahedral sites until a concentration threshold is obtained after which it starts to occupy the octahedral sites. In Mg:YIG films, due to the low concentration of Mg ions, only the tetrahedral sites are occupied. An experiment of the chemical sensitivity of a Ca-rich YIG film to reduction and oxydation solutions is also reported.

Reversible oxidation in calcium-substituted yttrium iron garnet epilayers

Reversible oxidation in calcium-substituted yttrium iron garnet epilayers

Domain observation in garnet films with the scanning electron microscope

The scanning electron microscope has been used successfully to detect magnetic contrast in garnet epilayers. Stripe domains of width < 10 μm are resolved in materials having 4π M s values in the range 200–440 G. A brief theoretical and experimental basis of the technique is presented.

A study of parameters to optimise the design of LPE dipping apparatus

The theoretical treatment of LPE growth of magnetic garnet materials by horizontal spinning has given good agreement between predicted and observed growth rates. However, for practical purposes it is necessary to obtain basic data for the solutions used; these include: the liquidus temperature, density, viscosity, diffusion coefficients, heat of crystallisation, and the variation (where appropriate) of these parameters with temperature and melt composition. Studies have been made on selected compositions in the system: PbO−B 2 O 3 −Y 2 O 3 −Eu 2 O 3 −Ga 2 O 3 −Fe 2 O 3 , and the results obtained are presented. The data acquired have been used to interpret the experimental results for LPE growth of magnetic garnet on GGG substrates. It is shown that good reproducibility is achievable provided attention is given in particular to the selection of suitable substrate rotation rates and values of undercooling. Consideration is also given to the effective segregation coefficients for the various constituents. The heat of crystallisation measured indicates that constituents may be present as separate oxide constituents in the melt, presumably as complexes with solvent constituents. The significance of this fact is used to explain in a qualitative manner the observed effective segregation coefficients. From the measured data and theoretical principles based on the Burton, Prim and Slichter model of a rotating disc, the practical requirements for growth equipment, suitable for laboratory scale controlled growth of garnet epilayers, are described. Practical details are given of the techniques used in the investigations described. The general approach of this work, concerned as it is with establishing the necessary preliminary data, should be particularly useful for studies on new solvent-solute systems.

Stress relief in magnetic garnet films grown by liquid phase epitaxy

Magnetic garnet epilayers with lattice parameters more than 0.041 larger than the nonmagnetic garnet substrates on which they were grown, are shown to be stress relieved and contain between 3×10 7 and 1×10 8 dislocations per cm 2 . The dislocations give rise to what has been called “faceting” in highly compressive films, and evidence suggests that they are half loops with misfit segments parallel to the interface. The misfit segments do not always lie at the interface, but rather their distance from the interface decreases with increasing mismatch, while the degree of stress relief in the dislocated films increases with increasing mismatch.

Analysis of substituted yttrium iron garnet epilayers by an electron microprobe

Quantitative analyses of garnet epilayers of the composition Y 3− x R x Fe 5− y Ga y O 12 with R = G d, S m or L a were done by a scanning electron microscope and an energy dispersive X-ray spectrometer. Using polycrystalline standards and with correction for the influence of the Gd 3Ga 5O 12 substrate on the Ga and Gd value the accuracy of the analysis is about 1% for y in the order of 1.2 and 2% for x in the order of 0.15.