Phase relation, crystal structures, and magnetic properties of Nd-Co-B borides
The phase relation of the ternary system Nd-Co-B quenched from 600 C in the Co-rich region has been determined by means of X-ray powder diffraction. In this region there exist 11 ternary borides. Five borides are members of the homologous series Nd{sub m+n}Co{sub 5m+3n}B{sub 2n} (or NdCo{sub 5{minus}x}B{sub x}). New layered borides Nd{sub 3}Co{sub 13}B{sub 2} and Nd{sub 5}Co{sub 19}B{sub 6} have not been reported previously. The space group of them is P6/mmm and their crystal structures are refined by the Rietveld method. All the compounds of this Nd{sub m+n}Co{sub 5m+3n}B{sub 2n} family magnetically order between T{sub C} = 710 K for Nd{sub 3}Co{sub 13}B{sub 2} and T{sub C} = 330 K for Nd{sub 2}Co{sub 7}B{sub 3}. The mean cobalt moments of the Nd{sub m+n}Co{sub 5m+3n}B{sub 2n} borides determined at 4.2 K are strongly dependent on the composition. On the basis of the experimental results, three kinds of Co sites with different magnetic moments are proposed. It is shown that increasing B content in NdCo{sub 5{minus}x}B{sub x} borides leads to an increase of the second-order crystal-field parameters A{sub 20}, which explains the enhancement of the magnetocrystalline anisotropy. Spin reorientations are observed in Nd{sub 3}Co{sub 13}B{sub 2} and Nd{sub 3}Co{sub 11}B{sub 4} compounds. The magnetic phase diagram of the Nd{sub m+n}Co{sub 5m+3n}B{sub 2n} borides is also given, and the behavior of magnetocrystalline anisotropy is analyzed using the single ion model.
- Research Organization:
- Chinese Academy of Sciences, Beijing (CN)
- OSTI ID:
- 20080262
- Journal Information:
- Chemistry of Materials, Vol. 12, Issue 5; Other Information: PBD: May 2000; ISSN 0897-4756
- Country of Publication:
- United States
- Language:
- English
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