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Title: Stability, Crystal Chemistry, and Magnetism of U 2+xNi 21–x\B 6 and Nb 3–yNi 20+yB 6 and the Role of Uranium in the Formation of the Quaternary U 2–zNb zNi 21B 6 and U δNb 3-δ Ni 20B 6 Systems

Abstract

In this work, we investigated the U–Ni–B and Nb–Ni–B systems to search for possible new heavy fermion compounds and superconducting materials. The formation, crystal chemistry, and physical properties of U 2Ni 21B 6 and Nb 3–yNi 20+yB 6 [ternary derivatives of the cubic Cr 23C 6-type ( cF116, $$Fm\bar{3}m$$)] have been studied; the formation of the hypothetical “U 3Ni 20B 6” and “Nb 2Ni 21B 6” has been disproved. U 2Ni 21B 6 [ a = 10.6701(2) Å] crystallizes in the ordered W 2Cr 21C 6-type, whereas Nb 3–yNi 20+yB 6 [ a = 10.5842(1) Å] adopts the Mg 3Ni 20B 6-type. Ni in U 2Ni 21B 6 can be substituted by U, leading to the solid solution U 2+xNi 21–xB 6 (0 ≤ x ≤ 0.3); oppositely, Nb in Nb 3Ni 20B 6 is partially replaced by Ni, forming the solution Nb 3–yNi 20+yB 6 (0 ≤ y ≤ 0.5), none of them reaching the limit corresponding to the hypothetically ordered “U 3Ni 20B 6” and “Nb 2Ni 21B 6”. These results prompted us to investigate quaternary compounds U 2–zNb zNi 21B 6 and U δNb 3-δNi 20B 6: strong competition in the occupancy of the 4 a and 8 c sites by U, Nb, and Ni atoms has been observed, with the 4 a site occupied by U/Ni atoms only and the 8 c site filled by U/Nb atoms only. U 2Ni 21B 6, U 2.3Ni 20.7B 6, and Nb 3Ni 20B 6 are Pauli paramagnets. Interestingly, Nb 2.5Ni 20.5B 6 shows ferromagnetism with TC ≈ 11 K; the Curie–Weiss fit gives an effective magnetic moment of 2.78 μ B/Ni, suggesting that all Ni atoms in the formula unit contribute to the total magnetic moment. The M(H) data at 2 K further corroborate the ferromagnetic behavior with a saturation moment of 10 μ B/fu (≈0.49 μ B/Ni). The magnetic moment of Ni at the 4 a site induces a moment in all of the Ni atoms of the whole unit cell ( 32f and 48h sites), with all atoms ordering ferromagnetically at 11 K. Density functional theory (DFT) shows that the formation of U 2Ni 21B 6 and Nb 3Ni 20B 6 is energetically preferred. The various electronic states generating ferromagnetism on Nb 2.5Ni 20.5B 6 and Pauli paramagnetism on U 2Ni 21B 6 and Nb 3Ni 20B 6 have been identified.

Authors:
ORCiD logo [1]; ORCiD logo [2];  [3];  [3]; ORCiD logo [4];  [5];  [6];  [7];  [1];  [8]; ORCiD logo [2];  [1]
  1. Univ. of Genova (Italy). Dept. of Chemistry
  2. Stockholm Univ. (Sweden). Dept. of Materials and Environmental Chemistry
  3. Ames Lab., and Iowa State Univ., Ames, IA (United States)
  4. Kurukshetra Univ., Haryana (India). Dept. of Physics
  5. Institute SPIN-CNR, Genova (Italy)
  6. Tata Inst. of Fundamental Research, Mumbai (India). Dept. of Condensed Matter Physics & Materials Science; Ramakrishna Mission Vivekananda Educational and Research Inst., West Bengal (India). Dept. of Physics
  7. Tata Inst. of Fundamental Research, Mumbai (India). Dept. of Condensed Matter Physics & Materials Science
  8. Univ. of Genova (Italy). Dept. of Physics
Publication Date:
Research Org.:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division
OSTI Identifier:
1574818
Report Number(s):
IS-J-10083
Journal ID: ISSN 0020-1669
Grant/Contract Number:  
AC02-07CH11358
Resource Type:
Accepted Manuscript
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 58; Journal Issue: 22; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Provino, Alessia, Smetana, Volodymyr, Hackett, Timothy A., Paudyal, Durga, Kashyap, Manish K., Bernini, Cristina, Bhattacharyya, Amitava, Dhar, Sudesh K., Pani, Marcella, Gatti, Flavio, Mudring, Anja-Verena, and Manfrinetti, Pietro. Stability, Crystal Chemistry, and Magnetism of U2+xNi21–x\B6 and Nb3–yNi20+yB6 and the Role of Uranium in the Formation of the Quaternary U2–zNbzNi21B6 and UδNb3-δ Ni20B6 Systems. United States: N. p., 2019. Web. doi:10.1021/acs.inorgchem.9b01440.
Provino, Alessia, Smetana, Volodymyr, Hackett, Timothy A., Paudyal, Durga, Kashyap, Manish K., Bernini, Cristina, Bhattacharyya, Amitava, Dhar, Sudesh K., Pani, Marcella, Gatti, Flavio, Mudring, Anja-Verena, & Manfrinetti, Pietro. Stability, Crystal Chemistry, and Magnetism of U2+xNi21–x\B6 and Nb3–yNi20+yB6 and the Role of Uranium in the Formation of the Quaternary U2–zNbzNi21B6 and UδNb3-δ Ni20B6 Systems. United States. doi:10.1021/acs.inorgchem.9b01440.
Provino, Alessia, Smetana, Volodymyr, Hackett, Timothy A., Paudyal, Durga, Kashyap, Manish K., Bernini, Cristina, Bhattacharyya, Amitava, Dhar, Sudesh K., Pani, Marcella, Gatti, Flavio, Mudring, Anja-Verena, and Manfrinetti, Pietro. Fri . "Stability, Crystal Chemistry, and Magnetism of U2+xNi21–x\B6 and Nb3–yNi20+yB6 and the Role of Uranium in the Formation of the Quaternary U2–zNbzNi21B6 and UδNb3-δ Ni20B6 Systems". United States. doi:10.1021/acs.inorgchem.9b01440.
@article{osti_1574818,
title = {Stability, Crystal Chemistry, and Magnetism of U2+xNi21–x\B6 and Nb3–yNi20+yB6 and the Role of Uranium in the Formation of the Quaternary U2–zNbzNi21B6 and UδNb3-δ Ni20B6 Systems},
author = {Provino, Alessia and Smetana, Volodymyr and Hackett, Timothy A. and Paudyal, Durga and Kashyap, Manish K. and Bernini, Cristina and Bhattacharyya, Amitava and Dhar, Sudesh K. and Pani, Marcella and Gatti, Flavio and Mudring, Anja-Verena and Manfrinetti, Pietro},
abstractNote = {In this work, we investigated the U–Ni–B and Nb–Ni–B systems to search for possible new heavy fermion compounds and superconducting materials. The formation, crystal chemistry, and physical properties of U2Ni21B6 and Nb3–yNi20+yB6 [ternary derivatives of the cubic Cr23C6-type (cF116, $Fm\bar{3}m$)] have been studied; the formation of the hypothetical “U3Ni20B6” and “Nb2Ni21B6” has been disproved. U2Ni21B6 [a = 10.6701(2) Å] crystallizes in the ordered W2Cr21C6-type, whereas Nb3–yNi20+yB6 [a = 10.5842(1) Å] adopts the Mg3Ni20B6-type. Ni in U2Ni21B6 can be substituted by U, leading to the solid solution U2+xNi21–xB6 (0 ≤ x ≤ 0.3); oppositely, Nb in Nb3Ni20B6 is partially replaced by Ni, forming the solution Nb3–yNi20+yB6 (0 ≤ y ≤ 0.5), none of them reaching the limit corresponding to the hypothetically ordered “U3Ni20B6” and “Nb2Ni21B6”. These results prompted us to investigate quaternary compounds U2–zNbzNi21B6 and UδNb3-δNi20B6: strong competition in the occupancy of the 4a and 8c sites by U, Nb, and Ni atoms has been observed, with the 4a site occupied by U/Ni atoms only and the 8c site filled by U/Nb atoms only. U2Ni21B6, U2.3Ni20.7B6, and Nb3Ni20B6 are Pauli paramagnets. Interestingly, Nb2.5Ni20.5B6 shows ferromagnetism with TC ≈ 11 K; the Curie–Weiss fit gives an effective magnetic moment of 2.78 μB/Ni, suggesting that all Ni atoms in the formula unit contribute to the total magnetic moment. The M(H) data at 2 K further corroborate the ferromagnetic behavior with a saturation moment of 10 μB/fu (≈0.49 μB/Ni). The magnetic moment of Ni at the 4a site induces a moment in all of the Ni atoms of the whole unit cell (32f and 48h sites), with all atoms ordering ferromagnetically at 11 K. Density functional theory (DFT) shows that the formation of U2Ni21B6 and Nb3Ni20B6 is energetically preferred. The various electronic states generating ferromagnetism on Nb2.5Ni20.5B6 and Pauli paramagnetism on U2Ni21B6 and Nb3Ni20B6 have been identified.},
doi = {10.1021/acs.inorgchem.9b01440},
journal = {Inorganic Chemistry},
number = 22,
volume = 58,
place = {United States},
year = {2019},
month = {11}
}

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