LOW-TEMPERATURE MAGNETIC-PROPERTIES OF NDXCO1-X AMORPHOUS THIN-FILMS

Amorphous thin films of NdxCo1−x alloys were prepared over the composition range 0.07 ⩽ x ⩽ 0.96 by the vacuum evaporation method with two heating sources. The field dependence of magnetization σ(H) in 0–7 T and at 1.5 K for all samples were investigated. The magnetic structure of these films were studied by magnetic measurement. It was found that the effective magnetic moment of the Co atom μCo = 1.87 ƒ(x)μB, ƒ(x) being the probability for bearing magnetic moment of cobalt atoms, the effective magnetic moment of the Nd atom μNd = 2.28μB for 0.07 ⩽ x ⩽ 0.50, and μNd = 2.28 - 1.76 (x − 0.50) for 0.50 ⩽ x ⩽ 0.96, and the maximum distribution angle ψO of magnetic moment of neodymium atoms is about 66° at x < 0.50 and ψO = 66° + 63.3° (x − 0.50) at x ⩾ 0.50. The temperature dependence of the magnetization σ(T) at 1.5−200 K with H = 7.0 T has been measured. When the neodymium concentration is larger than 24 at %, there is a sudden drop of σ(T) at about 20 K, and this temperature does not change with increase of Nd component. The results show that the demagnetized state of the amorphous Nd-Co films may be composed of asperomagnetic and speromagnetic structures. The sudden drop of σ(T) near 20 K for samples with x ⩾ 0.24 may be explained by the phase transition between speromagnetism and paramagnetism.