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

Abstract

We report on as tructural distortion of kinetically stable B 6 -based ferromagnetic Nb 6 FeIr 6 B 8 that induces an unprecedented transformation of aferromagnetic Fe chain into two ferrimagnetic Fe chains through superstructure formation. Density functional theory calculations showed that the ferromagnetic Fe-Fei ntrachain interactions found in the undistorted structure become ferrimagnetic in the distorted superstructure,m ainly because the two independent iron atoms building eachc hain interact antiferromagnetically and carry different magnetic moments.H igh-temperature SQUIDm agnetometry confirmed ferrimagnetic orderinga t5 25 Kw ith ah igh and negative Weiss constant of À972 Ki ndicating the presence of strong antiferromagnetic interactions,aspredicted. This finding paves the way for the development of lowdimensional magnetic intermetallic systems based on Heisenberg ferrimagnetic chains,which have previously been studied only in molecular-based compounds.Transition-metal-rich borides form an interesting class of compounds with aw ide range of crystal structures and interesting physical properties. [1][2][3][4][5][6][7][8][9][10][11] All these attributes have made borides ar ich playground for the creation of new compositions and structure types and for studying the influence of these structures on their physical properties. Thed ifferent physical properties of borides,l ike for other materials,are directly related to their crystal structure,which in the case of borides is influenced by the arrangement of boron atoms. [4] One such arrangement is the planar B 6 ring, first reported in the compound Ti 7 Rh 4 Ir 2 B 8 [12] and later found in several other phases,such as M 7 T 6 B 8 (M = Nb,T a; T= Ru, Rh, Ir), [13] Nb 6 Fe 1Àx Ir 6+x B 8 , [14] and M 7 Fe 3 B 8 (M = Nb,T a). [15] Although B n rings have been extensively studied in the gas phase,t hey are rare entities both in molecular-based and solid-state chemistry. [16][17][18][19][20] However,t hey were predicted by experimentalists and theoreticians studying gas-phase species[*] N.

POWGEN: rebuild of a third-generation powder diffractometer at the Spallation Neutron Source

“…Recently there has been great interest in measuring samples that have a rather large absorption cross section due to exciting quantum phenomena, such as topological insulators, Weyl metals and Kitaev spin liquids which are observed in heavier transition-metalcontaining compounds such as Ru, Rh, Os, Ir etc. (Sharma et al, 2018). Owing to the high intensity offered by the source and the increased detector coverage from the upgrade, it is now feasible to study somewhat higher absorbing samples using thinner (3 mm diameter) or annular cans (1 mm annulus).…”