Development Of Magnetic Anisotropy Research Articles

The role of surface to bulk ratio on the development of magnetic anisotropy in high Ga content Fe100-xGax thin films

In this work we show the development of bulk in-plane magnetic anisotropy in high Ga-content (Ga = 28 at. %) Fe100-xGax thin films as the layer thickness increases. This result is in clear contrast with the generally reported decrease of this anisotropy with the film thickness. We propose the interrelation between the enhancement of the Ga-pair correlations and a collinear distortion of the bcc structure within the sample plane as the origin of the magnetic anisotropy. Our results have been obtained by employing a combination of long and local range structural probe techniques with bulk and surface magnetic characterization techniques. The key point shown in this work is that the in-plane structural anisotropy and hence, the magnetic anisotropy, are developed as the layer thickness increases. This fact strongly suggests that the surface to bulk free energy ratio plays a key role in the formation of ordered phases with a distorted bcc cell in Fe100-xGax films with x around 28 at. %. Our work also shows the arising of new phenomena in these high Ga content alloys due to the close correlation between structural and magnetic properties.

Recognizing the threshold magnetic anisotropy for inclination shallowing: Implications for correcting inclination errors of sedimentary rocks

Post-depositional compaction is an integral part of sedimentary rock formation and thus has been reasonably deemed as a major culprit for the long-recognized inclination-shallowing problem in sedimentary rocks. Although theoretical treatment elegantly envisions magnetic anisotropy (or oblate fabrics) to correspond to the degree of compaction and the magnitude of inclination flattening, such correspondence has rarely been seen in nature quantitavely, which leaves the possibility of misidentification and/or over-correction for inclination shallowing using magnetic anisotropy. This is because the extent to which oblate magnetic fabrics are developed strongly enough for inclination to start becoming shallow is not yet known. Here, we present sedimentary paleomagnetic data from two ~6 m long gravity cores GHE24L and GHE27L from the northern slope of the South China Sea to examine the down-core changes in magnetic anisotropy and inclinations, and to explore the possible connection between the two parameters. The results show that oblate fabrics are dominantly developed at depths >~2m and the degree of anisotropy displays an overall gradual increase with depth. Inclination shallowing occurs in the > 5m segment of the relatively distal core GHE27L and the amount of shallowing largely correlates with the degree of anisotropy, suggesting a causal relation between the development of magnetic anisotropy and the degree of inclination shallowing. Examination of down-core changes in inclination and magnetic anisotropy suggests that a threshold anisotropy of PAMS~1.04 and PAAR~1.10 exists for inclination shallowing in the cores. For PAAR10° if particle anisotropy is <1.4. This study provides strong field evidence that complements and substantiates the theoretical model and suggests that the threshold anisotropy can be used as a first-order criterion to identify inclination errors of some sedimentary rocks.

Structural studies of some hydrogen-treated materials related to the HDDR-process of Nd/sub 2/Fe/sub 14/B-based alloys

Hydrogen-treated Nd/sub 14.0/Fe/sub 66.9/Co/sub 11.0/Ga/sub 1.0/Zr/sub 0.1/B/sub 7.0/ alloys have been examined by means of powder X-ray diffraction (XRD) and electron probe microanalysis (EPMA) to understand the mechanism of the development of magnetic anisotropy in the hydrogenation, decomposition, desorption, and recombination (HDDR) process of Nd/sub 2/Fe/sub 14/B-based alloys. It has been revealed that Nd/sub 2/Fe/sub 14/B phase can coexist in equilibrium with decomposed products, namely, /spl alpha/-Fe, NdH/sub 2/, and Fe/sub 2/B, in the presence of hydrogen of an atmospheric pressure over the temperature ranging 1113 to 1153 K. It was observed that Co and Ga condensed into a Nd/sub 2/Fe/sub 14/B phase during hydrogen-treatments, resulting in a thermodynamically stable Nd/sub 2/(Fe,Co,Ga)/sub 14/B compound. Well-developed anisotropic materials were obtained via the HDDR-process when the hydrogen-treatment was accomplished under such conditions that Nd/sub 2/(Fe,Co,Ga)/sub 14/B coexists with the decomposed products. All our results give a favorable support to the previous proposal that the crystallographic orientation of the original alloy can be conveyed via the undecomposed Nd/sub 2/Fe/sub 14/B particles through-out HDDR processing.

Formation of Fe 16N 2 and development of magnetic anisotropy in a FeN alloy

The effect of an applied stress on formation of Fe 16N 2 in a FeN alloy has been examined by use of a magnetic torque meter and a scanning electron microscope. Stress-assisted preferential nucleation of Fe 16N 2 and formation of metastable primary clusters have been detected by measuring magnetic anisotropy. It is found that uniaxial magnetization along the cube axis is not achieved in the early stage of precipitation, particularly during low temperature aging, but is achieved only after full aging at a higher temperature. On the basis of the analyses of magnetic torque curves, the possible structures of the primary clusters are proposed and compared with the microscopic observations of the precipitates.

Magnetic anisotropy of electrodeposited Co--P amorphous alloys

The development of magnetic anisotropy with regard to thickness in amorphous electrolytic Co-P alloys (15 at % P) has been observed in the range of thicknesses between 0.06-7.00μm. The study has been undertaken starting from the ratio M <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</inf> /M <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</inf> of the hysteresis loops. The results obtained indicate that for thicknesses below 4000 Å the samples show an axis of easy magnetization in the plane. In the case of greater thicknesses, the axis of easy magnetization develops gradually out of the plane, reaching a perpendicular position near 10 μm. Our results suggest that what we are dealing with here is a shape anisotropy such as that proposed by Cargill, III et al.

The Role of Vacancies and Interstitial Atoms in the Development of Magnetic Anisotropy

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