- Award ID(s):
- NSF-PAR ID:
- Date Published:
- Journal Name:
- Dalton Transactions
- Page Range / eLocation ID:
- 4323 to 4335
- Medium: X
- Sponsoring Org:
- National Science Foundation
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The synthesis, crystal structure determination, magnetic properties and bonding interaction analysis of a novel 3 d transition-metal complex, [CrBr 2 (NCCH 3 ) 4 ](Br 3 ), are reported. Single-crystal X-ray diffraction results show that [CrBr 2 (NCCH 3 ) 4 ](Br 3 ) crystallizes in space group C 2/ m (No. 12) with a symmetric tribromide anion and the powder X-ray diffraction results show the high purity of the material specimen. X-ray photoelectron studies with a combination of magnetic measurements demonstrate that Cr adopts the 3+ oxidation state. Based on the Curie–Weiss analysis of magnetic susceptibility data, the Néel temperature is found to be around 2.2 K and the effective moment (μ eff ) of Cr 3+ in [CrBr 2 (NCCH 3 ) 4 ](Br 3 ) is ∼3.8 µ B , which agrees with the theoretical value for Cr 3+ . The direct current magnetic susceptibility of the molecule shows a broad maximum at ∼2.3 K, which is consistent with the theoretical Néel temperature. The maximum temperature, however, shows no clear frequency dependence. Combined with the observed upturn in heat capacity below 2.3 K and the corresponding field dependence, it is speculated that the low-temperature magnetic feature of a broad transition in [CrBr 2 (NCCH 3 ) 4 ](Br 3 ) could originate from a crossover from high spin to low spin for the split d orbital level low-lying states rather than a short-range ordering solely; this is also supported by the molecular orbital diagram obtained from theoretical calculations.more » « less
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Transition‐metal borides (TMBs) containing B
n‐fragment ( n>3) have recently gained interest for their ability to enable exciting magnetic materials. Herein, we show that the B4‐containing TiFe0.64(1)Os2.36(1)B2is a new ferromagnetic TMB with a Curie temperature of 523(2) K and a Weiss constant of 554(3) K, originating from the chain of M3‐triangles ( M=64 %Fe+36 %Os). The new phase was synthesized from the elements by arc‐melting, and its structure was elucidated by single‐crystal X‐ray diffraction. It belongs to the Ti1+ xOs2− xRuB2‐type structure (space group P 2 m, no. 189) and contains trigonal‐planar B4boron fragments [B−B distance of 1.87(4) Å] interacting with M3‐triangles [ M–Mdistances of 2.637(8) Å and 3.0199(2) Å]. The experimental results were supported by computational calculations based on the ideal TiFeOs2B2composition, which revealed strong ferromagnetic interactions within and between the Fe3‐triangles. This discovery represents the first magnetically ordered Os‐rich TMB, thus it will help expand our knowledge of the role of Os in low‐dimensional magnetism of intermetallics and enable the design of such materials in the future.
Quantum spin systems such as magnetic insulators usually show magnetic order, but such classical states can give way to
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