The YCo₄B compound is known to crystalline in the CeCo₄B structure with an average Co magnetic moment of 0.7μ_B which is much smaller than the Co moment of 1.6μ_B in YCo₅. Previously, we have shown that the basal-plane anisotropy of Co in YCo₄B changes into easy-axis with increasing temperature (around 150K) or by substituting of La by Y. The present study has been carried out on free-powder and magnetically-aligned Y_1-xLa_xCo₄B samples with x=0.0, 0.2, 0.5, 0.8 and 1.0. Magnetisation measurements were performed at 4.2 K in low (static) fields (up to 4 T) and in high pulsed fields (up to 35 T). The main results are: i) up to 35 T, no transition is observed, the high-field susceptibility shows an induced Co moment of 0.004μ_B/T; ii) at 4.2 K the compounds with x=0.8 and 1.0 show easy-axis anisotropy, whereas the others have easy-plane anisotropy; iii) the saturation magnetisation is anisotropic with Δσ/σ_s values increasing from 0.008 for YCo₄B to 0.03 for LaCo₄B. This magnetisation anisotropy is compared to the ratio of the magnetocrystalline anisotropy energy and the exchange energy. © 1992.

Thuy N.P., Hong N.M., Liu J.P., Li X., Franse J.J.M., de Boer F.R.

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Từ khóa : Cobalt and Alloys - Magnetic Properties; Lanthanum Compounds - Magnetic Properties; Magnetic Properties - Analysis; Magnetization - Measurements; Cobalt Magnetic Moment; Exchange Energy; Magnetocrystalline Anisotropy Energy; Yttrium Compounds