AC SUSCEPTIBILITY OF THE FE(AL, CO) SYSTEM

The temperature and field dependence of the low-field ac susceptibilit y of the FeAl1-xCox (for 0. 1 less-than-or-equal-to x less-than-or-equ al-to 0.45) system are studied in the temperature range 160-300 K. The results of the chi'-T curves show broad maxima for samples with x les s-than-or-equal-to 0.3. The positions of the maxima for samples with x = 0.25 and 0.3 show a weak frequency dependence. For samples with x g reater-than-or-equal-to 0.3 the susceptibility continues to increase w ith temperature in the range studied. When an external transverse dc m agnetic field is applied, chi' decreases rapidly with increasing the m agnitude of the dc field for all studied samples. The obtained paramag netic temperature theta(p), increases rapidly with x. The results are discussed within the context of the Neel theory of superparamagnetism. The environmental effects on the magnetic moment of Fe and Co atoms a re used to interpret the results.