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Title: Magnetic Behaviour of Layered Ag(ll) Fluorides

Abstract

Fluoride phases that contain the spin-1/2 4d{sup 9} Ag(II) ion have recently been predicted to have interesting or unusual magnetochemistry, owing to their structural similarity to the 3d{sup 9} Cu(II) cuprates and the covalence associated with this unusual oxidation state of silver. Here we present a comprehensive study of structure and magnetism in the layered Ag(II) fluoride Cs{sub 2}AgF{sub 4}, using magnetic susceptometry, inelastic neutron scattering techniques and both X-ray and neutron powder diffraction. We find that this material is well described as a two-dimensional ferromagnet, in sharp contrast to the high-T{sub C} cuprates and a previous report in the literature. Analyses of the structural data show that Cs{sub 2}AgF{sub 4} is orbitally ordered at all temperatures of measurement. Therefore, we suggest that orbital ordering may be the origin of the ferromagnetism we observe in this material.

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
914003
Report Number(s):
BNL-78571-2007-JA
TRN: US0801466
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nat. Mater.; Journal Volume: 5
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; COVALENCE; CUPRATES; DIFFRACTION; FERROMAGNETISM; FLUORIDES; MAGNETISM; NEUTRONS; ORIGIN; SCATTERING; SILVER; NSLS; national synchrotron light source

Citation Formats

McLain,S., Dolgos, M., Tennant, D., Turner, J., Barnes, T., Proffen, T., Sales, B., and Bewley, R.. Magnetic Behaviour of Layered Ag(ll) Fluorides. United States: N. p., 2006. Web. doi:10.1038/nmat1670.
McLain,S., Dolgos, M., Tennant, D., Turner, J., Barnes, T., Proffen, T., Sales, B., & Bewley, R.. Magnetic Behaviour of Layered Ag(ll) Fluorides. United States. doi:10.1038/nmat1670.
McLain,S., Dolgos, M., Tennant, D., Turner, J., Barnes, T., Proffen, T., Sales, B., and Bewley, R.. Sun . "Magnetic Behaviour of Layered Ag(ll) Fluorides". United States. doi:10.1038/nmat1670.
@article{osti_914003,
title = {Magnetic Behaviour of Layered Ag(ll) Fluorides},
author = {McLain,S. and Dolgos, M. and Tennant, D. and Turner, J. and Barnes, T. and Proffen, T. and Sales, B. and Bewley, R.},
abstractNote = {Fluoride phases that contain the spin-1/2 4d{sup 9} Ag(II) ion have recently been predicted to have interesting or unusual magnetochemistry, owing to their structural similarity to the 3d{sup 9} Cu(II) cuprates and the covalence associated with this unusual oxidation state of silver. Here we present a comprehensive study of structure and magnetism in the layered Ag(II) fluoride Cs{sub 2}AgF{sub 4}, using magnetic susceptometry, inelastic neutron scattering techniques and both X-ray and neutron powder diffraction. We find that this material is well described as a two-dimensional ferromagnet, in sharp contrast to the high-T{sub C} cuprates and a previous report in the literature. Analyses of the structural data show that Cs{sub 2}AgF{sub 4} is orbitally ordered at all temperatures of measurement. Therefore, we suggest that orbital ordering may be the origin of the ferromagnetism we observe in this material.},
doi = {10.1038/nmat1670},
journal = {Nat. Mater.},
number = ,
volume = 5,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • Fluoride phases that contain the spin-1/2 4d{sup 9} Ag(II) ion have recently been predicted to have interesting or unusual magnetochemistry, owing to their structural similarity to the 3d{sup 9} Cu(II) cuprates and the covalence associated with this unusual oxidation state of silver. Here we present a comprehensive study of structure and magnetism in the layered Ag(II) fluoride Cs{sub 2}AgF{sub 4}, using magnetic susceptometry, inelastic neutron scattering techniques and both X-ray and neutron powder diffraction. We find that this material is well described as a two-dimensional ferromagnet, in sharp contrast to the high-T{sub c} cuprates and a previous report in themore » literature. Analyses of the structural data show that Cs{sub 2}AgF{sub 4} is orbitally ordered at all temperatures of measurement. Therefore, we suggest that orbital ordering may be the origin of the ferromagnetism we observe in this material.« less
  • The lanthanide coinage-metal diarsenides LnTAs{sub 2} (Ln=La, Ce-Nd, Sm; T=Ag, Au) have been reinvestigated and their structures have been refined from single crystal X-ray data. Two different distortion variants of the HfCuSi{sub 2} type are found: PrAgAs{sub 2}, NdAgAs{sub 2}, SmAgAs{sub 2}, GdAgAs{sub 2}, TbAgAs{sub 2}, NdAuAs{sub 2} and SmAuAs{sub 2} crystallize as twofold superstructures in space group Pmcn with the As atoms of their planar layers forming zigzag chains, whereas LaAgAs{sub 2}, CeAgAs{sub 2} and PrAuAs{sub 2} adopt a fourfold superstructure (space group Pmca) with cis-trans chains of As atoms. The respective atomic positions can be derived from themore » HfCuSi{sub 2} type by group-subgroup relations. The compounds with zigzag chains of As atoms exhibit metallic behaviour while those with cis-trans chains are semiconducting as measured on powder pellets. The majority of the compounds including 4f elements show antiferromagnetic ordering at T{sub N}<20 K. - Text3: Zigzig vs. cis-trans.« less
  • The synthesis of a high-purity sample of the layered oxide selenide Sr{sub 2}MnO{sub 2}Ag{sub 1.5}Se{sub 2} is reported. At ambient temperature it crystallises in the space group I4/mmm with two formula units in the unit cell and lattice parameters a=4.08771(1) Å, c=19.13087(8) Å. The compound displays mixed-valent manganese in a formal oxidation state close to +2.5 and powder neutron diffraction measurements reveal that below the Néel temperature of 63(1) K this results in an antiferromagnetic structure which may be described as A-type, modelled in the magnetic space group P{sub I}4/mnc (128.410 in the Belov, Neronova and Smirnova (BNS) scheme) inmore » which localised Mn moments of 3.99(2) μ{sub B} are arranged in ferromagnetic layers which are coupled antiferromagnetically. In contrast to the isostructural compound Sr{sub 2}MnO{sub 2}Cu{sub 1.5}S{sub 2}, Sr{sub 2}MnO{sub 2}Ag{sub 1.5}Se{sub 2} does not display long range ordering of coinage metal ions and vacancies, nor may significant amounts of the coinage metal readily be deintercalated using soft chemical methods. - Graphical abstract: Sr{sub 2}MnO{sub 2}Ag{sub 1.5}Se{sub 2} containing mixed valent Mn ions undergoes magnetic ordering with ferromagnetic coupling within MnO{sub 2} sheets and antiferromagnetic coupling between MnO{sub 2} sheets. - Highlights: • High purity sample of Sr{sub 2}MnO{sub 2}Ag{sub 1.5}Se{sub 2} obtained. • Magnetic structure determined. • Compared with related mixed-valent manganite oxide chalcogenides.« less
  • No abstract prepared.