Source Of Perpendicular Anisotropy Research Articles

Magnetic Force Microscopy on Nanocrystalline Co Films

Pioneer works in ultrathin magnetic films have shown perpendicular magnetic domains in the demagnetized state. The source of this perpendicular anisotropy is the interface anisotropy developed at the interface. Similar domains could be observed in tetragonally distorted ultrathin films due to the magnetoelastic anisotropy. On the other hand, single-crystalline hexagonal close packed (hcp) Co films when grown epitaxially with the c-axis oriented perpendicular to the film plane may show perpendicular stripe magnetic domains even up to a thickness of about 500 nm. In that case the source of perpendicular anisotropy was the magnetocrystalline anisotropy of bulk Co, which favors the c-axis. In this work, we have grown by radio frequency magnetron sputtering Co films in the thickness range 15-4500 nm. We have used various substrates, such as Corning glass, silicon and Al-foil. The substrate temperature was about 350 K. The films have been found by X-ray diffraction experiments to present various structures and textures depending on the preparation conditions, mainly the Ar-pressure and deposition rate. Stripe- and labyrinth-like domain configurations are observed in films textured along the c-axis, and in films with a mixture of hcp and fcc grains, repectively. Films which show mainly fcc or amorphous structure do not form perpendicular domains. The results are discussed with respect to magnetization loops.

Influence of Field-Annealing on the Magnetic Anisotropy of Amorphous Fe–Tb Films

Using torque magnetometry (TM), SQUID and TEM we have investigated a series of thin (50 to 80 nm) amorphous Tb0.28Fe0.72 films. A different influence on the magnetic anisotropy by field annealing at 323 to 873 K with magnetic field either perpendicular or parallel to the sample surface is found. The pair-ordering mechanism is believed to be the source of perpendicular anisotropy in amorphous Fe–Tb films which corresponds to results from measurements of pair distribution functions (pdfs) by in-situ-TEM experiments. Unidirectional anisotropy was found in the sample plane which corresponds to the orientation of the external magnetic field during the annealing process. The magnetic (TM) and structural (TEM) results obtained suggest that the unidirectional anisotropy is due to the tilt of the easy axis from the film normal as a consequence of dual magnetron sputtering.

On the nature of perpendicular anisotropy in sputtered GdCo thin films

The development of perpendicular anisotropy in amorphous GdCo based alloys is still not clearly understood, since no single model has been able to explain all of the various experimental results. This paper presents evidence that links the perpendicular magnetic anisotropy (Ku) in sputtered films with phase separation on a 25Å to 35Å scale as a function of bias. High resolution electron microscopy, large and small angle scattering by electrons, and Lorentz microscopy were combined in this study. Analogous to annealing E-beam evaporated pure GdCo in UHV [Herd, J. Appl. Phys. 49, (1978) 1744], the void network is seen to disappear at −50V bias. With a drop of the compensation point below room temperature, large perpendicular domains are observed at −100V bias, comparable to the development of Ku after the glass transition in evaporated and annealed films. Further increases of bias to −200V led to a decrease in strip width to 0.25μ. Application of bias in sputter deposition is seen to cause a continuous shift towards Co richer compositions, and simultaneously to effect annealing at increasing temperatures during deposition. Anisotropically shaped Co-rich clusters are thought to be the source of perpendicular anisotropy in GdCo based alloys in general. Some recent results on peak shape in diffraction patterns and argon incorporation into sputtered films are discussed.

3798. Phase separation as source of perpendicular anisotropy in amorphous GdCo. (USA): S R Herd,J appl Phys, 49 (3), 1978, 1744–1746

3798. Phase separation as source of perpendicular anisotropy in amorphous GdCo. (USA): S R Herd,J appl Phys, 49 (3), 1978, 1744–1746

Phase separation as source of perpendicular anisotropy in amorphous GdCo

The source of perpendicular anisotropy (PA) in 0.05 μ thick, evaporated amorphous GdCo films was investigated by correlating the magnetic domain structure, as observed in the Lorentz mode with film structure, as observed with high resolution electron microscopy and diffraction, as functions of post deposition in situ anneal and elevated substrate temperature. A strong void network was found to anneal out above 500 °K at an apparent glass transition. PA was developed either together with this or at slightly higher temperatures and could be correlated to the appearance of 60–100 Å wide columnar arrays of two separate amorphous phases. The phase separation is evident also in a splitting of the single broad diffraction peak, normally observed in homogeneous amorphous deposits without PA, into two distinct components. Deposition at substrate temperatures above this glass transition results in amorphous films which crystallize on annealing without development of PA. From this, PA is thought to arise from anisotropically shaped Co-rich regions in a transition stage between the homogeneous amorphous and crystalline states.