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Title: Doping Experiments on Low-Dimensional Oxides and a Search for Unusual Magnetic Properties of MgAlB14

Abstract

Doping experiments on La2CuO4, Sr2CuO3 and SrCu2(BO3)2 were performed with the intent of synthesizing new metallic low-=dimensional cuprate oxide compounds. Magnetic susceptibility χ(T) measurements on a polycrystalline La2CuO4 sample chemically oxidized at room temperature in aqueous NaClO showed superconductivity with a superconducting transition temperature Tc of 42.6 K and a Meissner fraction of 26%. They were unable to electrochemically oxidize La2CuO4 in a nonaqueous solution of tetramethylammonium hydroxide (TMAOH) and methanol. Sr2CuO3 was found to decompose upon exposure to air and water. Electron paramagnetic resonance, isothermal magnetization M(H), and χ(T) measurements on the primary decomposition product, Sr2Cu(OH)6, were consistent with a nearly isolated, spin S = 1/2, local moment model for the Cu+2 spins. From a fit of χ(T) by the Curie-Weiss law and of the M(H) isotherms by a modified Brillouin function, the weakly antiferromagnetic exchange interaction between adjacent Cu+2 spins in Sr2Cu(OH)6 was found to be J/kB = 1.06(4) K. Doping studies on SrCu2(BO3)2 were inconclusive. χ(T) measurements on an undoped polycrystalline sample of SrCu2(BO3)2, a sample treated with distilled water, and a sample treated with aqueous NaClO showed no qualitative differences between the samples. In addition, χ(T) and M(H, T) studies of the ultra-hard material MgAlB14 weremore » carried out in search of superconductivity or ferromagnetism in this compound. χ(T) measurements on a powder sample revealed temperature-independent diamagnetism from 1.8 K up to room temperature with a Curie-Weiss impurity concentration equivalent to ~ 1 mol% of spin-1/2 ions. In contrast, M(H, T) data on hot pressed samples showed evidence of ferromagnetic transitions above ~ 330 K. Scanning electron microscopy and Auger microprobe analysis of the hot pressed samples indicated that the observed ferromagnetism was likely due to Fe impurities.« less

Authors:
 [1]
  1. Iowa State Univ., Ames, IA (United States)
Publication Date:
Research Org.:
Ames Lab., Ames, IA (United States)
Sponsoring Org.:
USDOE Office of Science (US)
OSTI Identifier:
806588
Report Number(s):
IS-T 2066
TRN: US0301336
DOE Contract Number:  
W-7405-Eng-82
Resource Type:
Thesis/Dissertation
Resource Relation:
Other Information: TH: Thesis (Ph.D.); Submitted to Iowa State Univ., Ames, IA (US); PBD: 31 Dec 2002
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; CURIE-WEISS LAW; DIAMAGNETISM; ELECTRON SPIN RESONANCE; EXCHANGE INTERACTIONS; FERROMAGNETISM; HYDROXIDES; MAGNETIC PROPERTIES; MAGNETIC SUSCEPTIBILITY; OXIDES; SCANNING ELECTRON MICROSCOPY; SUPERCONDUCTIVITY; TRANSITION TEMPERATURE

Citation Formats

Hill, Julienne Marie. Doping Experiments on Low-Dimensional Oxides and a Search for Unusual Magnetic Properties of MgAlB14. United States: N. p., 2002. Web. doi:10.2172/806588.
Hill, Julienne Marie. Doping Experiments on Low-Dimensional Oxides and a Search for Unusual Magnetic Properties of MgAlB14. United States. https://doi.org/10.2172/806588
Hill, Julienne Marie. 2002. "Doping Experiments on Low-Dimensional Oxides and a Search for Unusual Magnetic Properties of MgAlB14". United States. https://doi.org/10.2172/806588. https://www.osti.gov/servlets/purl/806588.
@article{osti_806588,
title = {Doping Experiments on Low-Dimensional Oxides and a Search for Unusual Magnetic Properties of MgAlB14},
author = {Hill, Julienne Marie},
abstractNote = {Doping experiments on La2CuO4, Sr2CuO3 and SrCu2(BO3)2 were performed with the intent of synthesizing new metallic low-=dimensional cuprate oxide compounds. Magnetic susceptibility χ(T) measurements on a polycrystalline La2CuO4 sample chemically oxidized at room temperature in aqueous NaClO showed superconductivity with a superconducting transition temperature Tc of 42.6 K and a Meissner fraction of 26%. They were unable to electrochemically oxidize La2CuO4 in a nonaqueous solution of tetramethylammonium hydroxide (TMAOH) and methanol. Sr2CuO3 was found to decompose upon exposure to air and water. Electron paramagnetic resonance, isothermal magnetization M(H), and χ(T) measurements on the primary decomposition product, Sr2Cu(OH)6, were consistent with a nearly isolated, spin S = 1/2, local moment model for the Cu+2 spins. From a fit of χ(T) by the Curie-Weiss law and of the M(H) isotherms by a modified Brillouin function, the weakly antiferromagnetic exchange interaction between adjacent Cu+2 spins in Sr2Cu(OH)6 was found to be J/kB = 1.06(4) K. Doping studies on SrCu2(BO3)2 were inconclusive. χ(T) measurements on an undoped polycrystalline sample of SrCu2(BO3)2, a sample treated with distilled water, and a sample treated with aqueous NaClO showed no qualitative differences between the samples. In addition, χ(T) and M(H, T) studies of the ultra-hard material MgAlB14 were carried out in search of superconductivity or ferromagnetism in this compound. χ(T) measurements on a powder sample revealed temperature-independent diamagnetism from 1.8 K up to room temperature with a Curie-Weiss impurity concentration equivalent to ~ 1 mol% of spin-1/2 ions. In contrast, M(H, T) data on hot pressed samples showed evidence of ferromagnetic transitions above ~ 330 K. Scanning electron microscopy and Auger microprobe analysis of the hot pressed samples indicated that the observed ferromagnetism was likely due to Fe impurities.},
doi = {10.2172/806588},
url = {https://www.osti.gov/biblio/806588}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Jan 01 00:00:00 EST 2002},
month = {Tue Jan 01 00:00:00 EST 2002}
}

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