Intrinsic properties of stoichiometric LaFePO

摘要: DC and ac magnetization, resistivity, specific-heat, neutron-diffraction data reveal that stoichiometric LaFePO is metallic non-superconducting above $T=0.35\text{ }\text{K}$, with $\ensuremath{\gamma}=12.5\frac{\text{mJ}}{\text{mol}\text{ }{\text{K}}^{2}}$. Neutron-diffraction at room temperature $T=10\text{ }\text{K}$ are well described by the stoichiometric, tetragonal ZrCuSiAs structure, show no signs of structural distortions or long-range magnetic ordering to an estimated detectability limit $0.07{\ensuremath{\mu}}_{B}/\text{Fe}$. We propose a model based on shape iron-pnictide tetrahedron explains differences between LaFeAsO, parent compound recently discovered high-Tc oxyarsenides, which, in contrast, shows both spin-density wave transitions.