W. Iwamoto,
R.R. Urbano,
P.G. Pagliuso,
C. Rettori,
K. Samanta,
P. Bhattacharya,
R.S. Katiyar,
J.H.D. da Silva,
A. Pereira, Gd.M. Azevedo,
S.B. Oseroff
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ABSTRACT: Amorphous and crystalline thin films of Mn-doped (0.5%-10%) GaAs and crystalline thin films of Zn<sub>1-x</sub>Co<sub>x</sub>O(x= 3%-20%) were investigated by means of magnetic susceptibility and electron spin resonance (ESR). For the Mn-doped GaAs samples, our results show the absence of ferromagnetic ordering for the amorphous films in the 300>T>2 K temperature range, in contrast to the ferromagnetism found in crystalline films for T<sub>C</sub>< 110 K. A single ESR line with a temperature independent g-value (g~2) is observed for the amorphous films, and the behavior of this ESR linewidth depends on the level of crystallinity of the film. For the Mn-doped GaAs crystalline films, only a ferromagnetic mode is observed for T<T<sub>C</sub> when the film is ferromagnetic. Turning now the Zn<sub>1-x</sub>Co<sub>x</sub>O films, ferromagnetic loops were observed at room temperature for these films. The magnetization data show an increasing of the saturation magnetization M<sub>s</sub> as a function of x reaching a maximum value for xap10%. ESR experiments at T= 300 K in the same films show a strong anisotropic ferromagnetic mode (FMR) for x=0.10
IEEE Transactions on Magnetics 11/2006; · 1.36 Impact Factor
