Ultrahigh-vacuum growth techniques are now being used to grow single-crystal films of magnetic materials. These growth procedures, carried out in the same molecular beam epitaxy systems commonly used for the growth of semiconductor films, have yielded a variety of new materials and structures that may prove useful for integrated electronics and integrated optical device applications. Examples are given for growth on GaAs and ZnSe, including magnetic sandwiches and patterned structures.

https://science.sciencemag.org/content/sci/250/4984/1092.full.pdf

Hybrid ferromagnetic-semiconductor structures

Single‐crystal (100)Fe films 90–330 A thick have been grown on etch‐annealed (100)GaAs substrates by molecular‐beam‐epitaxy techniques. Ferromagnetic resonance data indicate that the two in‐plane 〈110〉 directions are inequivalent and, together with magnetometry data, show that the average film magnetization decreases as the thickness decreases. The inequivalence is attributed to the nature of the interface bonding at a (100) zinc‐blende surface. The decreased magnetization is attributed to the formation of Fe2As microclusters in the film due to As diffusion which is supported by Auger and electron diffraction studies. In general, the Fe films grown to date on etch‐annealed (100)GaAs substrates are significantly inferior to those grown on (110)GaAs.

Properties of Fe single‐crystal films grown on (100)GaAs by molecular‐beam epitaxy

Spin waves in periodic magnetic structures-magnonic crystals

Vue d'ensemble sur la preparation, la caracterisation, les proprietes de transport et les proprietes magnetiques des superreseaux

Artificial metallic superlattices

Nonreciprocal surface waves

This paper reviews the theory and potential applications of magnetically variable delay lines and oscillators which employ a magnetostrictive film on a piezoelectric surface-acoustic-wave (SAW) substrate. Cases analyzed in detail indicate that the delay change arises mainly from a rotation of the magnetic moment from the films' easy axes toward the applied field direction; thus the interaction is essentially nondispersive. Use of amorphous metallic-glass overlays is particularly attractive because their high magnetostriction and low magnetic anisotropy makes a relatively large delay variation possible with a small change in bias field. Since the SAW velocity can be changed only by \sim .1 % or less with present film technology, applications are restricted to those where only a small frequency or delay adjustment is required. Two prototype examples are considered in detail--a variable delay line for steering an adaptive array antenna and a tunable resonator oscillator capable of tracking high speed Doppler targets. In both of these examples, the magnetic film/SAW substrate geometry is seen to be an attractive alternative to competitive approaches.

Applications of amorphous magnetic-layers in surface-acoustic-wave devices

Interfacial effects in spin-wave resonance of iron films grown by molecular beam epitaxy

We have studied the symmetry properties of the in-plane induced magnetic anisotropy in {100} and {110} disks of single crystal YIG epitaxially grown on gadolinium gallium garnet (GGG) substrates. The ferromagnetic resonance (FMR) technique was used to determine the values of the cubic and induced magnetic anisotropies. The induced anisotropy is interpreted in terms of a magnetostrictive magnetic potential energy. We find that the effective field induced in the plane of the film is isotropic for {100} disks but for {110} disks the induced anisotropy is uniaxial within the plane.

Induced in-plane magnetic anisotropy in YIG films

We have developed a mathematical formulation by which surface-impedance calculations of magnetic layered structures are significantly simplified and, hence, calculable. A transfer-function matrix is introduced in order to relate the electric and magnetic fields at one surface of a magnetic metal layer to fields at the other surface. The surface impedance of a layered structure is then expressed in terms of the four transfer-function matrix elements corresponding to surface fields of the layered structure instead of internal microwave fields corresponding to all the layers within the layered structure. The ferromagnetic resonance fields and line shapes are calculated for layered structures containing alternating dielectric and iron magnetic layers. In addition, spin-pinning boundary conditions are assumed at the surfaces of each iron layer. The calculations are of sufficient generality so that the insulating dielectric layer may be replaced by a conductive metal layer. We find that standing spin-wave resonance may be excited in the layered structure, even for zero spin pinning at the iron-layer surfaces. From calculations of internal microwave fields within each layer, we deduce that the spin-wave resonance is due to an asymmetrical magnetic field excitation of each iron layer, although the layered structure as a whole is symmetrically excited. For iron-layer thicknesses of \ensuremath{\ge}1500 A\r{} there is no discernible difference between the ferromagnetic resonance fields of the main line and the first-spin-wave\char21{}resonance mode\char22{}an accidental degeneracy. If nonzero spin pinning is assumed at each iron-layer surface, the accidental degeneracy is removed.

Ferromagnetic and transmission resonance in magnetic metal superlattices.

Magnetostatic surface wave (MSSW) propagation loss and ferrimagnetic resonance linewidth of thin films of liquid phase epitaxy yttrium iron garnet were measured in the frequency range 2 to 9 GHz. With increasing frequency, both the loss and linewidth initially decreased to a minimum value at about 3 GHz and thereafter increased linearly with frequency. The measurements are in agreement with recent predictions of Vittoria and Wilsey; namely, there is a direct correspondence between MSSW propagation loss and magnetic damping at all frequencies.

C. Vittoria

Papers

Applications of amorphous magnetic-layers in surface-acoustic-wave devices

Interfacial effects in spin-wave resonance of iron films grown by molecular beam epitaxy

Induced in-plane magnetic anisotropy in YIG films

Ferromagnetic and transmission resonance in magnetic metal superlattices.

Magnetostatic propagation in thin films of liquid phase epitaxy YIG