Neutron-diffraction study of the Nd_n+1Co_3n+5B_2n compounds

Abstract.

The crystal and magnetic structures of the Nd_n+1Co_3n+5B_2n (n=1, 2 and 3) compounds have been studied by high-resolution powder neutron diffraction at the Institut Laue Langevin. The results are compared to earlier measurements on the isotype Y_n+1Co_3n+5B_2n compounds. The neutron-diffraction analysis shows that the magnetic moments are ferromagnetically ordered. The magnetic structures of NdCo₄B, Nd₃Co₁₁B₄ and Nd₂Co₇B₃ confirm that a large variety of magnetic moments exist for the cobalt atoms. On the one hand, the magnetic behavior of the cobalt atoms situated in the 2c position is not significantly affected by the substitution of boron for cobalt. On the other hand, the cobalt atoms situated on the 3g, 6i₁ and 6i₂ positions are carrying significantly reduced magnetic moments in comparison with those of the Co (2c) ones. The Nd magnetic moments are also found to be sensitive to the boron content. Finally, the direction of easy magnetization is found to be unchanged upon boron for cobalt substitution and lies in the basal plane for NdCo₄B, Nd₃Co₁₁B₄ and Nd₂Co₇B₃.