Magnetic correlations and their dependence on excess oxygen in La sub 2 NiO sub 4+. delta. (DK)

Journal Article · Sun Sep 01 00:00:00 EDT 1991 · Physical Review, B: Condensed Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.44.5046· OSTI ID:5295435

Freltoft, T ^[1]; Buttrey, D J ^[2]; Aeppli, G ^[3]; Vaknin, D ^[4]; Shirane, G ^[5]

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1. Corporate R D, NKT, DK-2605 Brondby (Denmark)
2. Department of Chemical Engineering, Colburn Laboratory, University of Delaware, Newark, Delaware (USA)
3. AT T Bell Laboratories, 600 Mountain Avenue, Murray Hill, New Jersey (USA)
4. Physics Department, Riso National Laboratory, DK-4000 Roskilde (Denmark)
5. Brookhaven National Laboratory, Upton, New York (USA)

We report results of elastic- and inelastic-neutron-scattering studies of three single crystals of the layered perovskite La{sub 2}NiO{sub 4+{delta}}, with {delta}=0.00, 0.067, and 0.077, as well as neutron powder diffraction on a material with an oxygen excess {delta}{approx}0.065. The magnetic correlations are highly sensitive to the oxygen content, and three-dimensional antiferromagnetic order sets in at {ital T}{sub {ital N}}{ge}300 K, and {ital T}{sub {ital N}}=68, and 48 K for the single crystals, respectively, and at {ital T}{sub {ital N}}=74 K for the powder sample. The crystal with {delta}=0.067 was studied in detail to characterize the tetragonal to orthorhombic ({ital T}{sub {ital s}}=232--240 K) and antiferromagnetic ({ital T}{sub {ital N}}=68 K) transitions. The order parameter {eta}({ital T}) for the orthorhombic distortion shows a power-law dependence on temperature with the exponent {beta}=0.21 and hysteresis, suggesting that this transition is less than second order. Two-dimensional critical scattering is observed around the antiferromagnetic phase transition. The magnetic excitation spectra in the three-dimensional ordered state are characterized by small anisotropy gaps between {similar to}0 and 3 meV, and large effective in-plane spin-wave velocities, which decrease with increasing {delta}. For {delta}=0.077, {ital c}{approx}130 meV A; and for {delta}=0.00, {ital c}{ge}300 meV A.

• DOE Contract Number: AC02-76CH00016
• OSTI ID: 5295435
• Journal Information: Physical Review, B: Condensed Matter; (United States), Vol. 44:10; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
LANTHANUM OXIDES
MAGNETIC PROPERTIES
NICKEL OXIDES
CORRELATIONS
MONOCRYSTALS
NEUTRON DIFFRACTION
OXYGEN
QUANTITY RATIO
STOICHIOMETRY
CHALCOGENIDES
COHERENT SCATTERING
CRYSTALS
DIFFRACTION
ELEMENTS
LANTHANUM COMPOUNDS
NICKEL COMPOUNDS
NONMETALS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
SCATTERING
TRANSITION ELEMENT COMPOUNDS
360104* - Metals & Alloys- Physical Properties