Structural and magnetic properties of the single-layer manganese oxide La{sub 1-x}Sr{sub 1+x}MnO{sub 4}

Journal Article · Sat Jan 01 00:00:00 EST 2005 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.71.024435· OSTI ID:20665043

Larochelle, S; Vajk, O P ^[1]; Mehta, A; Kaneko, N; Zhou, L ^[2]; Lu, L; Mang, P K ^[3]; Lynn, J W ^[4]; Greven, M ^[2]

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1. Department of Physics, Stanford University, Stanford, California 94305 (United States)
2. Stanford Synchrotron Radiation Laboratory, Stanford Linear Accelerator Center, Stanford, California 94309 (United States)
3. Department of Applied Physics, Stanford University, Stanford, California 94305 (United States)
4. NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)

Using x-ray and neutron scattering, we have studied the structural and magnetic properties of the single-layer manganite La{sub 1-x}Sr{sub 1+x}MnO{sub 4}(0{<=}x<0.7). Single crystals were grown by the floating-zone method at 18 La/Sr concentrations. The low-temperature phase diagram can be understood by considering the strong coupling of the magnetic and orbital degrees of freedom, and it can be divided into three distinct regions: low (x<0.12), intermediate (0.12{<=}x<0.45), and high (x{>=}0.45) doping. LaSrMnO{sub 4}(x=0) is an antiferromagnetic Mott insulator, and its spin-wave spectrum is well described by linear spin-wave theory for the spin-2 square-lattice Heisenberg Hamiltonian with Ising anisotropy. Upon doping, as the e{sub g} electron concentration (1-x) decreases, both the two-dimensional antiferromagnetic spin correlations in the paramagnetic phase and the low-temperature ordered moment decrease due to an increase of frustrating interactions, and Neel order disappears above x{sub c}=0.115(10). The magnetic frustration is closely related to changes in the e{sub g} orbital occupancies and the associated Jahn-Teller distortions. In the intermediate region, there exists neither long-range magnetic nor superstructural order. Short-range-correlated structural 'nanopatches' begin to form above x{approx}0.25. At high doping (x{>=}0.45), the ground state of La{sub 1-x}Sr{sub 1+x}MnO{sub 4} exhibits long-range superstructural order and a complex antiferromagnetic order, which differs from that at low doping. The superstructural order is thought to arise from charge and orbital ordering on the Mn sites, and for x=0.50 we conclude that it is of B2mm symmetry. For x>0.50, the superstructural order becomes incommensurate with the lattice, with a modulation wave vector {epsilon} that depends linearly on the e{sub g} electron concentration: {epsilon}=2(1-x). On the other hand, the magnetic order remains commensurate, but loses its long-range coherence upon doping beyond x=0.50.

• OSTI ID: 20665043
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Vol. 71, Issue 2; Other Information: DOI: 10.1103/PhysRevB.71.024435; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANTIFERROMAGNETIC MATERIALS
ANTIFERROMAGNETISM
HAMILTONIANS
HEISENBERG MODEL
ISING MODEL
JAHN-TELLER EFFECT
LANTHANUM COMPOUNDS
LAYERS
MAGNETIC PROPERTIES
MANGANESE OXIDES
NEUTRON DIFFRACTION
PHASE DIAGRAMS
SPIN WAVES
STRONG-COUPLING MODEL
STRONTIUM COMPOUNDS
X-RAY DIFFRACTION
ZONE MELTING