Short- and long-range magnetic order in LaMnAsO

Article

关键词: LAYERED SUPERCONDUCTOR;    COLOSSAL MAGNETORESISTANCE;    METAL;    TRANSITION;    INSULATOR;    CRYSTAL;    LA;    GD;    CO;    SM;   

DOI  :  10.1103/PhysRevB.93.054404

来源: SCIE

【 摘 要 】

The magnetic properties of the layered oxypnictide LaMnAsO have been revisited using neutron scattering and magnetization measurements. The present measurements identify the Neel temperature T-N = 360(1) K. Below T-N the critical exponent describing the magnetic order parameter is beta = 0.33-0.35, consistent with a three-dimensional Heisenberg model. Above this temperature, diffuse magnetic scattering indicative of short-range magnetic order is observed, and this scattering persists up to T-SRO = 650(10) K. The magnetic susceptibility shows a weak anomaly at T-SRO and no anomaly at T-N. Analysis of the diffuse scattering data using a reverse Monte Carlo algorithm indicates that above T-N nearly two-dimensional, short-range magnetic order is present with a correlation length of 9.3(3) angstrom within the Mn layers at 400 K. The inelastic scattering data reveal a spin gap of 3.5 meV in the long-range ordered state, and strong, low-energy (quasielastic) magnetic excitations emerging in the short-range ordered state. Comparison with other related compounds correlates the distortion of the Mn coordination tetrahedra to the sign of the magnetic exchange along the layer-stacking direction, and suggests that short-range order above T-N is a common feature in the magnetic behavior of layered Mn-based pnictides and oxypnictides.

【 授权许可】

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