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Title: Eu 2+ –Eu 3+ valence transition in double, Eu-, and Na-doped PbSe from transport, magnetic, and electronic structure studies

The Eu atoms in Pb 1-xEu xSe have long been assumed to be divalent. We show that p-type doping of this magnetic semiconductor alloy with Na can modify the effective Eu valence: a mixed, Eu 2+–Eu 3+ state appears in Pb 1-x-yEu xNa ySe at particular values of y. Magnetization, carrier concentration, resistivity, and thermopower of Pb 1-x-yEu xNa ySe are reported for a number of samples with different x and y. A pronounced increase in thermopower at a given carrier concentration was identified and attributed to the presence of enhanced ionized impurity scattering. A strong decrease in the hole concentration is observed in Pb1-yNaySe when Eu is added to the system, which we attribute to a Eu 2+–Eu 3+ self-ionization process. This is evidenced by magnetization measurements, which reveal a significant reduction of the magnetic moment of Pb 1-xEu xSe upon alloying with Na. Further, a deviation of magnetization from a purely paramagnetic state, described by a Brillouin function, identifies antiferromagnetic interactions between the nearest-neighbor Eu atoms: a value of J ex/k B = -0.35 K was found for the exchange coupling parameter. The conclusion of a Eu 2+–Eu 3+ self-ionization process being in effect is supported further bymore » the electronic structure calculations, which show that an instability of the 4f 7 configuration of the Eu 2+ ion appears with Na doping. In conclusion, schematically, it was found that the Eu 4f levels form states near enough to the Fermi energy that hole doping can lower the Fermi energy and trigger a reconfiguration of a 4f electronic shell.« less
Authors:
ORCiD logo [1] ;  [2] ;  [3] ;  [2] ;  [4] ;  [3] ;  [4] ;  [5]
  1. AGH Univ. of Science and Technology, Krakow (Poland). Faculty of Physics and Applied Computer Science; The Ohio State Univ., Columbus, OH (United States). Dept of Mechanical & Aerospace Engineering
  2. The Ohio State Univ., Columbus, OH (United States). Dept of Mechanical & Aerospace Engineering
  3. Northwestern Univ., Evanston, IL (United States). Dept. of Chemistry
  4. Michigan State Univ., East Lansing, MI (United States). Dept. of Chemical Engineering and Materials Science
  5. The Ohio State Univ., Columbus, OH (United States). Dept of Mechanical & Aerospace Engineering, and Dept. of Physics
Publication Date:
Grant/Contract Number:
SC0001054; W911NF-14-1-0016; 1433467
Type:
Accepted Manuscript
Journal Name:
Physical Chemistry Chemical Physics. PCCP (Print)
Additional Journal Information:
Journal Name: Physical Chemistry Chemical Physics. PCCP (Print); Journal Volume: 19; Journal Issue: 14; Journal ID: ISSN 1463-9076
Publisher:
Royal Society of Chemistry
Research Org:
Michigan State Univ., East Lansing, MI (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF); Polish National Science Centre (NCN)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE
OSTI Identifier:
1425681