Magnetic properties of LaCo13-based systems

Abstract

Four polycomponent systems based on LaCo₁₃ have been studied: La(Co_1−xFe_x)₁₃, La(Co_1−xAl_x)₁₃, La(Co_1−x−yFe_xAl_y)₁₃, and La_0.7Nd_0.3(Co_0.7Fe_0.3)₁₃. These 1:13 systems were studied because of their potential for permanent magnet fabrication. LaCo₁₃ has a high 3d metal content, the highest for any known rare‐earth intermetallic, a 13 kG saturation induction, and a high T_c (1318 K). Unfortunately, it is cubic and lacks anisotropy. The substituted systems were examined as a portion of a program to find LaCo₁₃‐based systems of applications significance. Replacement of Co in LaCo₁₃ by Fe and/or Al leads to a rapid decline in T_c for all systems studied. Replacement of Co by Al results in a decline in moment, whereas replacement by Fe leads to a rise in moment to 2.39μ_B/3d atom for La(Co_0.4Fe_0.6)₁₃, as compared to 2.46μ_B/3d atom for Fe_0.7Co_0.3. Analysis of the magnetic data shows that vacancies occur in both half‐bands for LaCo₁₃ (4.8 spin up and 3.24 spin down) but in only one half‐band in La(Co_1−xAl_x)₁₃ for x≥0.2. Nd in these systems carries a moment of 3μ_B, close to that of the free tripositive ion.