Abstract
A large change is observed in the magnetic properties of amorphous Fe–Zr thin films sputtered at different Ar pressures. The change depends on the composition of the alloys and at compositions near 60 at.% Fe, for example, the magnetisation measured at 10 kOe increases 30-fold with an increase in the Ar pressure from 2 to 10 mTorr. The magnetic properties are well explained by a combination of two phenomena—superparamagnetism and spin glass behaviours—and the large change is partly related to the number density of a magnetically correlated region. Examinations of the microstructure by X-ray diffraction, transmission electron microscopy, and X-ray absorption fine structure spectroscopy reveal no appreciable difference in it as a function of the Ar pressure. This indicates that even a very slight change in the microstructure can greatly affect the magnetic properties of amorphous Fe–Zr thin films, thereby opening up the possibility of employing the magnetic properties of amorphous alloys for the characterisation of amorphous microstructures.
Highlights
PAr and number of Fe chips on alloy target
For a given number of Fe chips, the CFe value decreases with increasing PAr, because Fe is lighter than Zr and subjected to a greater degree of thermalization at a higher PAr value
A prominent point to be noted from the results shown in Fig. 1 is that the magnetisation is highly sensitive to PAr; this is true when the CFe value is large
Summary
PAr (horizontal axis) and number of Fe chips on alloy target (vertical axis). The numeral in each loop denotes the CFe value. In order to understand the relationship between the degree of amorphization and the magnetic properties more clearly, a systematic study was conducted that involved fabrication of amorphous Fe–Zr alloy thin films over a wide composition range and characterisation of these films both structurally and magnetically. Thin films of amorphous Fe–Zr alloys have found important applications in the control of the texture and surface roughness as a way to improve the related magnetic and magnetotransport properties[15,16]. Despite this practical importance of these alloys, their magnetic properties are not clearly understood at present. A clear understanding of the relationship between the degree of amorphization and the magnetic properties of amorphous Fe–Zr alloys will be of great theoretical and practical importance
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