Anomalous Behavior of Localized Magnetic Moments in Itinerant Ferromagnets Ln₂Co₁₂P₇ (Ln = Y, Pr, Nd, Sm, Gd and Dy)

Abstract

We synthesized polycrystalline samples of ternary compounds Ln₂Co₁₂P₇ (Ln = Y, Pr, Nd, Sm, Gd and Dy) with the Curie temperature being about 150 K and measured magnetization to clarify magnetism of Co sublattice and also to clarify behavior of magnetic moments of Ln³⁺ in ferromagnetic phase. As a result, magnetism of Y₂Co₁₂P₇ was found to be a possible weakly itinerant electronic ferromagnetism and found to be similar to that of Lu₂Co₁₂P₇, indicating that magnetism of Co sublattice does not change with Ln. From results for Ln₂Co₁₂P₇, we found that spin components of magnetic moments of Ln³⁺ ferromagnetically couple with exchange field of ferromagnetic moments of Co sublattice. This result means that behavior of magnetic moments of Ln³⁺ can be described as the single ion model applied to the permanent magnets (LnCo₅, Ln₂Fe₁₄B etc.) though the sign of coupling constant is opposite of the cases of permanent magnets. This is because magnetic moments of Co and Ln couple through P, not a direct coupling in cases of permanent magnets.