TY - JOUR
T1 - Metastable β-NdCo2B2
T2 - A Triclinic Polymorph with Magnetic Ordering
AU - Powderly, Kelly M.
AU - Guo, Shu
AU - Mitchell Warden, Hillary E.
AU - Nguyen, Loi T.
AU - Cava, R. J.
N1 - Funding Information:
The authors thank Austin Ferrenti for information on band structure calculations, Dr. Daniel Straus for discussions about DSC and kinetics of reactions, and Dr. Elizabeth Carnicom for advice on arc melting boride compounds. This research was partially supported by the National Science Foundation (NSF) through the Princeton University Materials Research Science and Engineering Center DMR-1420541 (K.M.P. and L.T.N.) and by the Taylor Fellowship through the Edward C. Taylor Graduate Fund in Chemistry (K.M.P.). K.M.P. also acknowledges the support of the NSF Graduate Research Fellowship under grant no. DGE-1656466. The crystal structure refinement (S.G.) and DFT calculations (H.E.M.W.) were supported as part of the Institute for Quantum Matter, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award no. DE-SC0019331. The authors acknowledge the use of Princeton’s Imaging and Analysis Center, which is partially supported by the Princeton Center for Complex Materials, a NSF-MRSEC program (DMR-1420541).
Publisher Copyright:
© 2021 American Chemical Society.
PY - 2021/8/24
Y1 - 2021/8/24
N2 - Metastable phases increase the diversity of structure-property relationships, facilitating the study and comparison of materials. In this article, we present the synthesis and characterization of a metastable polymorph of NdCo2B2, synthesized by arc melting, which we designate as β-NdCo2B2. Single-crystal X-ray diffraction reveals that it crystallizes in a new triclinic structure type with space group P1¯ (#2). The structure is composed of 3D Co-B channels filled by Nd zig zags, a large departure from the thermodynamically stable tetragonal ThCr2Si2-type polymorph. β-NdCo2B2 is closely related to the BaRh2Si2 structure type, providing a connection to the "122-type"channel-containing RM2B2 compounds (R = rare-earth element, M = Ni, Ru, Os, and Ir) that was previously absent for rare-earth cobalt borides of this stoichiometry. Differential scanning calorimetry shows that this new polymorph transforms irreversibly into the tetragonal form upon heating above 530 °C. β-NdCo2B2 displays metallic conductivity and magnetically orders into a complex ferromagnetic or ferrimagnetic state at 7.7 K. We present density functional theory calculations throughout to further explore the stability, magnetism, and electronic structure. β-NdCo2B2 demonstrates that new compounds with interesting structural and magnetic properties can be found even in well-studied chemical systems, such as the ternary transition metal borides.
AB - Metastable phases increase the diversity of structure-property relationships, facilitating the study and comparison of materials. In this article, we present the synthesis and characterization of a metastable polymorph of NdCo2B2, synthesized by arc melting, which we designate as β-NdCo2B2. Single-crystal X-ray diffraction reveals that it crystallizes in a new triclinic structure type with space group P1¯ (#2). The structure is composed of 3D Co-B channels filled by Nd zig zags, a large departure from the thermodynamically stable tetragonal ThCr2Si2-type polymorph. β-NdCo2B2 is closely related to the BaRh2Si2 structure type, providing a connection to the "122-type"channel-containing RM2B2 compounds (R = rare-earth element, M = Ni, Ru, Os, and Ir) that was previously absent for rare-earth cobalt borides of this stoichiometry. Differential scanning calorimetry shows that this new polymorph transforms irreversibly into the tetragonal form upon heating above 530 °C. β-NdCo2B2 displays metallic conductivity and magnetically orders into a complex ferromagnetic or ferrimagnetic state at 7.7 K. We present density functional theory calculations throughout to further explore the stability, magnetism, and electronic structure. β-NdCo2B2 demonstrates that new compounds with interesting structural and magnetic properties can be found even in well-studied chemical systems, such as the ternary transition metal borides.
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U2 - 10.1021/acs.chemmater.1c01545
DO - 10.1021/acs.chemmater.1c01545
M3 - Article
AN - SCOPUS:85113680159
SN - 0897-4756
VL - 33
SP - 6374
EP - 6382
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 16
ER -