Effects of Annealing Temperature on Co30Cu70 Mechanical Alloys

Watcharee RATTANASAKULTH; Chitnarong SIRISATHITKUL

Authors

Watcharee RATTANASAKULTH Department of Physics, Faculty of Science, Kasetsart University, Bangkok 10900
Chitnarong SIRISATHITKUL Magnet Laboratory, Molecular Technology Research Unit, School of Science, Walailak University, Nakhon Si Thammarat 80161

Keywords:

Giant magnetoresistance, mechanical alloying, annealing

Abstract

Physical properties of Co₃₀Cu₇₀ mechanical alloys prepared by ball milling were investigated. After milling for 50 h, the powder contained Co-rich, Cu-rich clusters as well as Co-Cu solid solution. Annealing at 200 - 300°C for 30 min modified thermal behaviors but only slightly affected magnetic properties. Higher temperature annealing (400 - 500°C) led to substantial oxidation of Co and Cu and deteriorated magnetic properties. Pressed Co₃₀Cu₇₀pellets exhibited 0.6 - 2 % giant magnetoresistance (GMR) but showed modest GMR after heat treatment. GMR disappeared by annealing at 500 °C as large fractions of Co and Cu were converted into oxides.

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