Paul J. Besser

A stress model for heteroepitaxial magnetic oxide films grown by chemical vapor deposition

Abstract A simple physical model is presented which predicts the sign and magnitude of stress in heteroepitaxial films. The model explains experimental observations of ferromagnetic resonance, domain structure, and crazing in magnetic oxide films grown by chemical vapor deposition (CVD) on non-magnetic substrates. It provides a means of predicting and developing compatible film-substrate combinations for epitaxial bubble domain materials utilizing a stress-induced uniaxial magnetic anisotropy. A basic result of the model, the conditions under which films can be grown in compression, has been verified experimentally for CVD iron garnets.

Mobile Cylindrical Magnetic Domains in Epitaxial Garnet Films

The properties of cylindrical domains in wafers of bulk single crystals of various magnetic oxides have been extensively studied and described in recent months. Mobile cylindrical domains have been produced in single‐crystal thin films of gallium‐substituted yttrium iron garnet. The deposits are formed by chemical vapor deposition onto nonmagnetic garnet substrates greater than 1 cm2 in area. A model of magnetic anisotropy in epitaxial films is proposed and shown to be in good agreement with experimental domain observations. In a typical sample, a domain diameter of 8 μ is observed in a 6‐μ‐thick film at a bias field of 25 Oe. From the domain translational velocity of 5600 cm/sec, a cylindrical domain mobility of 1500 cm/sec Oe has been calculated. A fractional change in cylindrical domain diameter of −0.07%/°K has been measured at 300°K. Annealing at 1570°K for several hours did not alter the Neel temperature or the optical transmission spectrum.

Ferromagnetic resonance properties of LPE YIG films

This is the first report of the ferromagnetic resonance properties of thin single-crystal YIG films grown by liquid phase epitaxy techniques (LPE). The resonance linewidths of photoetched disks are close to that of bulk YIG for both parallel and perpendicular resonance without any annealing of the films. A new type of surface spin wave, localized at the air-film interface, is shown to exist in perpendicular resonance. The boundary conditions necessary for this surface spin wave to exist are produced either by SiO 2 sputtering or ion implantation.

New approaches to hard bubble suppression

Since the discovery of hard bubbles [1,2], several techniques for their suppression have been reported [3,4]. This paper describes a new double-layer method which is more versatile than previously reported suppression techniques. It is also shown that it may be possible to prevent hard bubble generation without resorting to exchange coupling of multi-layer films. This study has also produced interesting evidence that it is only the generation of hard bubbles that is suppressed, not their existence. The latter result indicates that the existing model of hard bubble suppression [5] is incomplete.

Substrate facet replication by epitaxial magnetic garnet films

Abstract Epitaxial ferrimagnetic garnet films were deposited on Czochralski grown single crystal gadolinium gallium garnet substrates containing faceted regions. Films grown by both chemical vapor deposition (CVD) and liquid phase epitaxy (LPE) were studied. Lattice parameter distributions were determined by the method of X-ray double crystal topography with rocking curve analysis. The demagnetized domain strip width, magnetization, and characteristic length were measured in a CVD film in regions inside and outside the substrate facets. It was determined that replication of the substrate facets by the epitaxial film is accomplished by a difference in film stress. This stress difference arises from the lattice parameter difference between the faceted and unfaceted regions of the substrate. These results lead to the establishment of a criterion for allowable lattice parameter variation in substrates to be used for magnetic bubble domain films with stress induced anisotropy.

Orientation Dependence of Spin‐Wave Spectra in Single‐Crystal YIG Films

Spin‐wave resonance in epitaxial films of yttrium iron garnet (YIG) has been studied as a function of the orientation of the static field H relative to the film plane and the crystallographic axes. The positions, intensities, and linewidths of the main branch and the higher branches have been measured in (100) and (110) disks with thicknesses from 0.37 to 1.15 μ. Higher branches which are spaced more than ∼100 Oe from the main branch in perpendicular resonance (H⊥film, θ = 90°) disappear between θ = 90° and θ = 0°, while those which are closer are present over the entire range of θ. In a 0.37‐μ, (100) film the first higher branch disappears at θ = 49°. It reappears one degree on either side of this critical angle and is spaced ∼50 Oe from the main line at these points. The linewidth of the first higher branch reaches a maximum of 7.1 Oe near θ = 49° and decreases to values of 2.0 and 2.4 Oe at θ = 90° and 0°, respectively. The main branch linewidth increases monotonically from 1.8 to 7.1 Oe between θ = 90...

Characteristics of epitaxial garnets grown by CVD using single metal alloy source

Single metal alloys have been explored as the cation source in the chemical vapor deposition (CVD) of iron garnets. Growth of good quality single crystal garnet films containing as many as five different cations has been achieved over a wide range of deposition conditions. The relationship of film composition to alloy compositions and deposition conditions has been determined for several materials. By proper choice of the alloy composition and the deposition conditions, uncrazed deposits were grown on