Ternary borides Nb₇Fe₃B₈ and Ta₇Fe₃B₈ with Kagome-type iron framework

Abstract

Two new ternary borides TM7Fe3B8 (TM = Nb, Ta) were synthesized by high-temperature thermal treatment of samples obtained by arc-melting. This new type of structure with space group P6/mmm, comprises TM slabs containing isolated planar hexagonal [B6] rings and iron centered TM columns in a Kagome type of arrangement. Chemical bonding analysis in Nb7Fe3B8 by means of the electron localizability approach reveals two-center interactions forming the Kagome net of Fe and embedded B, while weaker multicenter bonding present between this net and Nb atoms. Magnetic susceptibility measurements reveal antiferromagnetic order below TN = 240 K for Nb7Fe3B8 and TN = 265 K for Ta7Fe3B8. Small remnant magnetization below 0.01μB per f.u. is observed in the antiferromagnetic state. The bulk nature of the magnetic transistions was confirmed by the hyperfine splitting of the Mössbauer spectra, the sizable anomalies in the specific heat capacity, and the kinks in the resistivity curves. The high-field paramagnetic susceptibilities fitted by the Curie-Weiss law show effective paramagnetic moments μeff≈ 3.1μB/Fe in both compounds. The temperature dependence of the electrical resistivity also reveals metallic character of both compounds. Density functional calculations corroborate the metallic behaviour of both compounds and demonstrate the formation of a sizable local magnetic moment on the Fe-sites. They indicate the presence of both antiferro- and ferrromagnetic interactions.

R8-xRu3In7+x, R3Ru1-xIn3, R39Ru12-xIn35, and R16Ru5In14 (R=La-Nd, Sm, Gd-Er, Lu) - New ternary indides with 2D intergrowth of CsCl- and AlB2-related slabs

“…4). Likewise, atomic arrangement in some transition metal borides such as [8], Nb 7 Fe 3 B 8 [30], Ru 9 Al 5 B 8-x [31,32], Fe 3 Al 2 B 2 [31], and Ru 4 Al 3 B 2 [32] can be described as T m+n T' m B 2n family members built of a 2D intergrowth of TB 2 fragments of AlB 2type and TT' fragments of CsCl-type ( Fig. 4).…”

Structural‐Distortion‐Driven Magnetic Transformation from Ferro‐ to Ferrimagnetic Iron Chains in B6‐based Nb6FeIr6B8

“…The different physical properties of borides, like for other materials, are directly related to their crystal structure, which in the case of borides is influenced by the arrangement of boron atoms . One such arrangement is the planar B 6 ring, first reported in the compound Ti 7 Rh 4 Ir 2 B 8 and later found in several other phases, such as M 7 T 6 B 8 (M=Nb, Ta; T=Ru, Rh, Ir), Nb 6 Fe 1− x Ir 6+ x B 8 , and M 7 Fe 3 B 8 (M=Nb, Ta) . Although B n rings have been extensively studied in the gas phase, they are rare entities both in molecular‐based and solid‐state chemistry .…”

Structural Evolution and Chemical Bonding of Diniobium Boride Clusters Nb2Bx–/0 (x = 1–6): Hexagonal‐Bipyramidal Nb2B6–/0 Species

“…The planar and quasiplanar boron clusters are often associated with aromaticity which can enhance the stability of the planar framework of small boron rings , , . Recently, a planar B 6 ring was creatively observed and synthesized in the solid phase, which suggests that planar boron clusters can be potential building blocks in bulk boride compounds and can also shed light on studies of new classes of borometallic complexes.…”