Positive exchange bias in amorphous ErCo 2: Evidence of coexistence of ferromagnetic and antiferromagnetic subdomains

Abstract

Magnetization measurements have been carried out on an amorphous ErCo 2 thin film in the temperature range 4–400 K. M versus H cycles exhibit a positive exchange bias developing gradually as the temperature is lowered, beginning at 400 K, which is the highest available temperature. The temperature dependence of the magnetization in the earth's field and H = 1 kOe have been accounted for on the basis of antiferromagnetic exchange coupling between erbium and cobalt atoms and the existence of a positive exchange bias. Positive exchange bias may arise from the exchange interaction at microscopic interfaces between the antiferromagnetically (AF) correlated subdomains and the ferromagnetically (FM) correlated subdomains of Er atoms. At temperatures below 50 K, we see evidence for long range sperimagnetic-like ordering.