Impedance, magnetoimpedance and magnetization of CoFeZr nanoclusters embedded into alumina matrix
|Alexander K. Fedotov 2, Saad Anis 3, I. A. Svito 2, Julia A. Fedotova 2, Bogdan V. Andrievsky 1, Yury E. Kalinin 5, Alexy A. Patryn 1, Vera V. Fedotova 4, Victoria Malyutina-Bronskaya 2, Alexander V. Mazanik 2, Alexander V. Sitnikov 5, Maria I. Tarasik 2|
1. Technical University of Koszalin, Raclawicka 15-17, Koszalin, Poland
The 3 to 5 mcm thick films with the fraction x of CoFeZr alloy between 30 and 65 at.% in alumina matrix were sputtered on single substrate from the compound target in the chamber evacuated either with pure Ar or Ar-O gas mixture.
It was also revealed by Mössbauer spectroscopy and magnetization measurements that phase composition and magnetic state of metallic component strongly depends on gas mixture in the sputtering chamber: metallic nanoclusters in the samples sputtered in pure Ar displayed magnetic properties whereas at sputtering in Ar-O gas mixture they were superparamagnetic. We connect this difference with the influence of oxide precipitates formed on metallic nanoparticles due to the presence of oxygen in gas mixture in the sputtering chamber.
Real part of impedance versus temperature R(T) exhibited exponential laws characteristic for hopping mechanisms. It was also exhibited negative sign of R(B) with squared-like magnetic field dependence that can be ascribed to tunneling of carriers by localized states in alumina between metallic nanoparicles. For the samples with the metallic alloy concentration 40 at.% < x < 55 at.% R does not depend significantly on frequency f in the temperature range where it shows activational temperature dependences (as for DC resistance). For the samples with x < 40 at.% the R(f) ~ f in -s extent with s ~ 2 for temperatures less than 120 K and activational temperature dependences only for f < 400 kHz. For the samples over the percolative threshold (x > 55 at.%) the R(f) ~ f in -s extent dependence is disturbed although exponential character of impedance is remained.
Presentation: oral at E-MRS Fall Meeting 2005, Symposium D, by Alexander K. Fedotov
See On-line Journal of E-MRS Fall Meeting 2005
Submitted: 2005-05-16 17:14 Revised: 2009-06-07 00:44