Robert John Kobliska

Amorphous ferromagnetic thin films

Amorphous ferromagnetic thin films containing one or more transition metals and one or more glass formers have been fabricated by sputtering. Typical magnetic properties of these thin films are comparable to those of bulk amorphous alloys with corresponding compositions. Thermal stability and annealing characteristics of these amorphous thin films are discussed.

Magnetocrystalline anisotropy in epitaxially grown (Gd,Tm,Y)3(Fe,Ga)5O12 garnet thin films

Single‐crystal thin films of gallium‐substituted mixed garnets (Gd,Tm,Y)3(Fe,Ga)5O12, grown by liquid phase epitaxy, have been used as drive layer materials in contiguous disk bubble devices; a critical parameter for the selection of a specific composition is the value of the magnetocrystalline anisotropy constant K1. We have measured the values of K1 in a series of epitaxial thin films grown on (100) and (111) oriented gadolinium gallium garnet substrates. K1 in the (100) oriented films were measured both by ferrimagnetic resonance and with an inductive hysteresigraph, whereas only resonance measurements were employed in the (111) oriented films. The values of K1 for each composition, obtained by different methods from films with different orientations, agree reasonably well with each other and are consistent with what would be expected from linear extrapolation of the K1’s of pure rare‐earth iron garnets after an empirical correction for gallium substitution.

Annealing behavior of amorphous ferromagnetic Co‐Fe‐B and Fe‐B thin films

The annealing behavior of amorphous Co‐Fe‐B and Fe‐B thin films, fabricated by rf sputtering in an argon plasma, have been investigated. The magnetostrictive Fe‐B films exhibit a perpendicular anisotropy in the as‐deposited condition, but after a stress relief anneal an in‐plane anisotropy is obtained. An in‐plane easy axis develops in the as‐deposited Co‐Fe‐B thin films. The in‐plane anisotropy direction in both sets of films can be rotated by annealing in an external magnetic field aligned parallel to the hard axis via a thermally activated process. Preannealing with a magnetic field aligned parallel to the easy axis stabilizes these films to a significant extent. The kinetics of easy axis rotation has a simple logarithmic dependence on time. Analysis of the kinetics of easy axis rotation indicates that preannealing apparently increases the thermal activation energy for this rotation process.

Abstract: Magnetocrystalline anisotropy in mixed garnet thin films

We have measured the values of K1 in films grown on (100) and (111) oriented gadolinium gallium garnet substrates from PbO:B2O3:Fe2O3 fluxed melts. The values of K1 for each composition, obtained by different methods from films with different orientations, are consistent within themselves but are significantly smaller in magnitude than what would be expected from linear extrapolation of the K1’s of pure rare earth‐iron garnets. (AIP)

Abstract: Annealing behavior of amorphous ferromagnetic Co‐Fe‐B and Fe‐B thin films

The annealing behavior of amorphous Co‐Fe‐B and Fe‐B thin films, fabricated by RF sputtering in an Ar plasma, has been investigated. (AIP)

Abstract: Spin wave resonance in amorphous ferrimagnetic GdCoMoAr alloy film

Spin wave resonances, observed in an amorphous Gd6.9Co74Mo12.8Ar6.3 ferrimagnetic alloy film, indicate that the exchange stiffness constant, A, decreases rapidly with increasing temperature. By extension of spin‐wave theory to ferrimagnets, the temperature dependence of A has been interpreted in terms of a two sub‐network ferrimagnet.(AIP)