Structural and magnetization density studies of La sub 2 NiO sub 4

Journal Article · Fri Sep 01 00:00:00 EDT 1989 · Physical Review (Section) B: Condensed Matter; (USA)

DOI:https://doi.org/10.1103/PhysRevB.40.4463· OSTI ID:5524902

Lander, G H ^[1]; Brown, P J ^[2]; Spalek, J; Honig, J M ^[3]

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1. Commission of European Communities, Joint Research Centre, Postfach 2340, D-7500 Karlsruhe, Federal Republic of Germany (DE)
2. Institut Laue-Langevin 156X, 38042 Grenoble CEDEX, France
3. Department of Physics and Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-3699

Neutron diffraction experiments have been performed on single crystals of La{sub 2}NiO{sub 4}. Above 70 K the structure is orthorhombic {ital Bmab}. At 70 K a first-order transition occurs to a crystal structure that we believe to be tetragonal {ital P}4{sub 2}/ncm. With our resolution we see no splitting of the diffraction peaks that would indicate the lower-symmetry orthorhombic {ital Pccn}. A crystallographic refinement of 307 independent reflections from two different crystals gives an {ital R} factor of 6% for the {ital P}4{sub 2}/ncm phase. The refinement also shows that our crystals are stoichiometric with an oxygen composition of 4.02{plus minus}0.03. The crystals are antiferromagnetic with a magnetic structure in which the propagation and spin directions are parallel to (100), in agreement with other studies. The antiferromagnetic ordered moment at {ital T}=10 K is (1.62{plus minus}0.05){mu}{sub {ital B}} per Ni atom. According to susceptibility measurements {ital T}{sub {ital N}}{congruent}650 K on stoichiometric La{sub 2}NiO{sub 4}, but we have not checked this in our neutron experiment. No change in the antiferromagnetic structure occurs at the 70-K transition, but we cannot exclude the formation of a 2{bold k} magnetic structure at this temperature that would give rise to the same diffraction pattern in the tetragonal phase. In the second part of our experiment the induced magnetic form factor ({ital H}=4.6 T, applied parallel to the (010) axis at 5 K) has been measured with polarized neutrons. Our object in this experiment was to search for covalency effects, in particular evidence of interaction between the Ni {ital d}{sub {ital x}{sup 2}{minus}{ital y}{sup 2}} orbital and the {ital p}{sub {ital x}}, {ital p}{sub {ital y}} orbitals of the oxygens in the Ni-O plane.

• OSTI ID: 5524902
• Journal Information: Physical Review (Section) B: Condensed Matter; (USA), Journal Name: Physical Review (Section) B: Condensed Matter; (USA) Vol. 40:7; ISSN 0163-1829; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360204* -- Ceramics
Cermets
& Refractories-- Physical Properties
656100 -- Condensed Matter Physics-- Superconductivity
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANTIFERROMAGNETIC MATERIALS
BEAMS
CHALCOGENIDES
COHERENT SCATTERING
CRYSTAL STRUCTURE
CRYSTALS
DIFFRACTION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
LOW TEMPERATURE
MAGNETIC MATERIALS
MAGNETIC PROPERTIES
MAGNETIZATION
MATERIALS
MONOCRYSTALS
NEUTRON DIFFRACTION
NICKEL COMPOUNDS
NICKEL OXIDES
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POLARIZED BEAMS
RARE EARTH COMPOUNDS
SCATTERING
SUPERCONDUCTIVITY
TRANSITION ELEMENT COMPOUNDS