Magnetic softening of young's modulus of amorphous Fe90Zr10
Abstract The Young's modulus and the internal friction of amorphous Fe90Zr10 alloy were measured near the Curie temperature using the vibrating reed technique. The modulus shows softening around Tc(= 227 K) and the internal friction undergoes drastic increase in the same temperature range. It is found that both the Young's modulus and the reciprocal of internal friction are inversely proportional to the magnetic susceptibility in the paramagnetic phase.
Magnetoelastic study of amorphous Fe90+xZr10-x alloys
Abstract Young's modulus ( E ) of stress-relieved Fe-rich Fe–Zr amorphous alloys has been measured as a function of temperature in the range 80–350 K using the vibrating reed technique. The measured E ( T ) data are corrected for thermal expansion and non-magnetic background, E bg ( T ), to arrive at the magnetic contribution to Young's modulus, Δ E / EE bg =[ E ( T )− E bg ( T )]/ E ( T ) E bg ( T ), in the ferromagnetic state. A strikingly different behaviour of Δ E / EE bg is observed in alloys whose Fe content differs barely by 1 at% in that Δ E / EE bg decreases monotonously in amorphous (a-) Fe 90 Zr 10 , whereas after an initial decrease it increases steeply in a-Fe 91 Zr 9 as the temperature is lowered from the Curie point ( T C ) down to 80 K. Generalisation of the Landau theory of phase transitions leads to an expression for Δ E / EE bg that includes both first- and second-order magnetoelastic contributions, which respectively are linear and quadratic in stress. This expression is shown to provide a straightforward explanation for the distinctly different behaviour of Δ E / EE bg observed in a-Fe 90 Zr 10 and a-Fe 91 Zr 9 alloys. Furthermore, the present theoretical approach not only brings out clearly the role of exchange-enhanced local spin-density fluctuations in the thermal demagnetisation of spontaneous magnetisation but also permits an accurate determination of the pressure dependence of T C from the Young's modulus measurements on systems (which exhibit strong magnetoelastic effects) such as the alloys in question.
Studies of thermally-oxidized GaAs by transmission electron microscopy
Abstract Thermally oxidized GaAs has been examined using transmission electron microscopy to determine the structure and phases of the resulting oxide films. At growth temperatures of 500°C and above, the films were composed mainly of twinned poly-crystalline β-Ga 2 O 3 , the amount of crystallinity increasing with growth temperature. An amorphous oxide film was formed at a low growth temperature (450°C). No arsenic-containing phases were detected in any oxide film.