Magnetic moments in amorpous palladium-cobalt-silicon alloys

[摘要] The magnetic moments of amorphous ternary alloys containing Pd,Co and Si in atomic concentrations corresponding to Pd_(80-x)Co_xSi_(20) inwhich x is 3, 5, 7, 9, 10 and 11, have been measured between 1.8 and300°K and in magnetic fields up to 8.35 kOe. The alloys were obtainedby rapid quenching of a liquid droplet and their structures wereanalyzed by X-ray diffraction. The measurements were made in a null-coilpendulum magnetometer in which the temperature could bevaried continuously without immersing the sample in a cryogenic liquid.The alloys containing 9 at.% Co or less obeyed Curie's Law over certaintemperature ranges, and had negligible permanent moments at roomtemperature. Those containing 10 and 11 at.% Co followed Curie's Lawonly above approximately 200°K and had significant permanent momentsat room temperature. For all alloys, the moments calculated fromCurie's Law were too high to be accounted for by the moments of individualCo atoms. To explain these findings, a model based on theexistence of superparamagnetic clustering is proposed. The clustersizes calculated from the model are consistent with the rapid onset offerromagnetism in the alloys containing 10 and 11 at.% Co and with themagnetic moments in an alloy containing 7 at.% Co heat treated in sucha manner as to contain a small amount of a crystalline phase. Inalloys containing 7 at.% Co or less, a maximum in the magnetization vstemperature curve was observed around 10°K. This maximum was eliminatedby cooling the alloy in a magnetic field, and an explanation forthis observation is suggested.

[发布机构] University:California Institute of Technology;Department:Engineering and Applied Science

[关键词] Materials Science