Boron: Enabling Exciting Metal-Rich Structures and Magnetic Properties

Abstract

Boron's unique chemical properties and its reactions with metals have yielded the large class of metal borides with compositions ranging from the most boron-rich YB (used as monochromator for synchrotron radiation) up to the most metal-rich NdFeB (the best permanent magnet to date). The excellent magnetic properties of the latter compound originate from its unique crystal structure to which the presence of boron is essential. In general, knowing the crystal structure of any given extended solid is the prerequisite to understanding its physical properties and eventually predicting new synthetic targets with desirable properties. The ability of boron to form strong chemical bonds with itself and with metallic elements has enabled us to construct new structures with exciting properties. In recent years, we have discovered new boride structures containing some unprecedented boron fragments (trigonal planar B units, planar B rings) and low-dimensional substructures of magnetically active elements (ladders, scaffolds, chains of triangles). The new boride structures have led to new superconducting materials (e.g., NbRuB) and to new itinerant magnetic materials (e.g., NbFeIrB). The study of boride compounds containing chains (Fe-chains in antiferromagnetic ScFeRuB), ladders (Fe-ladders in ferromagnetic TiFeRhB), and chains of triangles (Cr chains in ferrimagnetic and frustrated TiCrIrB) of magnetically active elements allowed us to gain a deep understanding of the factors (using density functional theory calculations) that can affect magnetic ordering of such low-dimensional magnetic units. We discovered that the magnetic properties of phases containing these magnetic subunits can be drastically tuned by chemical substitution within the metallic nonmagnetic network. For example, the small hysteresis (measure of magnetic energy storage) of TiFeRhB can be successively increased up to 24-times by gradually substituting Ru for Rh, a result that was even surpassed (up to 54-times the initial value) for Ru/Ir substitutions. Also, the type of long-range magnetic interactions could be drastically tuned by appropriate substitutions in the metallic nonmagnetic network as demonstrated using both experimental and theoretical methods. It turned out that Ru-rich and valence electron poor metal borides adopting the TiCoB or the ThFe structure types have dominating antiferromagnetic interactions, while in Rh-rich (or Ir-rich) and valence electron rich phases ferromagnetic interactions prevail, as found, for example, in the ScFeRuRhB and FeRhRuB series. Fascinatingly, boron clusters (e.g., B rings) even directly interact in some cases with the magnetic subunits, an interaction which was found to favor the Fe-Fe magnetic exchange interactions in the ferromagnetic NbFeIrB. Using less expensive transition metals, we have recently predicted new itinerant magnets, the experimental proof of which is still pending. Furthermore, new structures have been discovered, all of which are being studied experimentally and computationally with the aim of...

Thermal conductivity of PrRh4.8B2, a layered boride compound

“…[1][2][3][4][5][6][7] Regarding properties, many studies have been carried out into the magnetism of borides, [7][8][9][10][11][12][13][14] and recent especial efforts have been made to develop the high temperature thermoelectric properties of novel borides. [15][16][17][18][19][20] Being refractory materials, thermoelectric borides have the potential to be used in high impact energy-saving applications like topping cycles for power plants and waste heat power generation in industry.…”

A Delicate Balance between Antiferromagnetism and Ferromagnetism: Theoretical and Experimental Studies of A2MRu5B2 (A=Zr, Hf; M=Fe, Mn) Metal Borides

“…[1][2][3][4][5][6][7][8][9] Besides these more common properties, some metal boridesa re superconductors, such as MgB 2 [10] (first high-temperature metallic superconductor) or the recently discovered NbRuB, [11] Ta RuB, or NbOsB, [12] whereas several others show great stabilitya gainst neutron or otherr adiation types, for example, YB 66 , [13] which is used as am onochromatorf or synchrotron radiation.M oreover, many metal borides are known for their extraordinary magnetic (e.g.,N d 2 Fe 14 B 2 ), magnetocaloric (e.g.,A lFe 2 B 2 ), and thermoelectric properties. [1][2][3][4][5][6][7][8][9] Besides these more common properties, some metal boridesa re superconductors, such as MgB 2 [10] (first high-temperature metallic superconductor) or the recently discovered NbRuB, [11] Ta RuB, or NbOsB, [12] whereas several others show great stabilitya gainst neutron or otherr adiation types, for example, YB 66 , [13] which is used as am onochromatorf or synchrotron radiation.M oreover, many metal borides are known for their extraordinary magnetic (e.g.,N d 2 Fe 14 B 2 ), magnetocaloric (e.g.,A lFe 2 B 2 ), and thermoelectric properties.…”

Simple, Green, and High‐Yield Production of Boron‐Based Nanostructures with Diverse Morphologies by Dissolution and Recrystallization of Layered Magnesium Diboride Crystals in Water

“…The element boron has alwaysi ntrigued the scientific community on account of its rich inherentp roperties-low density, high mechanical strength but lighter weight, high thermal resistance, high specific resistancea to rdinary temperature, high meltingp oint, ability to absorb neutrons, and high resistance to chemical attack. [1][2][3][4][5][6] Recent advances in the science of twodimensional( 2D) materials have motivated researchers to investigatet he prospects of realizing planar nanostructures constitutedf rom boron. [5,[7][8][9][10][11][12][13] Such nanoconstructs are expectedt o serve as promising platforms for utilizing the inherent properties of boron to their full potential.…”