Superconductivity, spin-glass properties, and ferromagnetism in amorphous La-Gd-Au alloys

[摘要] The superconducting and magnetic properties of splat cooled amorphous alloys of composition (La_100-xGd_x)₈₀Au₂₀ (0 ≤ x ≤ 100)have been studied. The La₈₀Au₂₀ alloys are ideal type II super-conductors(critical temperature T_c = 3.5° K ). The concentrationrange (x less than 1) where superconductivity and spin-glass freezing n1ightcoexist has been studied in detail. The spin-glass alloys (0 less than x less than 70)exhibit susceptibility maxima and thermomagnetic history effects.In the absence of complications due to crystal field and enhancedmatrix effects, a phenomenological model is proposed in which themagnetic clusters are treated as single spin entities interacting viarandom forces using the molecular field approach. The fundamentalparameters (such as the strength of the forces and the size ofclusters) can be deduced from magnetization measurements. Theremanent magnetization is shown to arise from an interplay of theRKKY and dipolar forces. Magnetoresistivity results are found to beconsistent with the aforementioned picture. The nature of magneticinteractions in an amorphous matrix is also discussed. The momentper Gd atom (7µ_B) is found to be constant and close to that of thecrystalline value throughout the concentration range investigated.Finally, a detail study is made of the critical phenomena andmagnetic properties of the amorphous ferromagnet: Gd₈₀Au₂₀. Theresults are compared with recent theories on amorphous magnetism.

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

[关键词] Applied Physics