Electron energy-loss spectroscopy and ab initio electronic structure of the LaOFeP superconductor

TL;DR

This study combines theoretical calculations and experimental electron energy loss spectroscopy to analyze the electronic structure and superconductivity of LaOFeP, revealing weak magnetism, doping effects, and orientation-dependent spectral features.

Contribution

It provides a comprehensive analysis of LaOFeP's electronic structure using first principles calculations and EELS measurements, including effects of doping and orientation dependence.

Findings

Fe atom shows weak magnetic moment and no long-range magnetic order

Low oxygen pressure enhances superconductivity in LaOFeP

Orientation affects the EELS spectral features, especially at 44 eV

Abstract

The electronic band structures of the LaOFeP superconductor have been calculated theoretically by the first principles method and measured experimentally by electron energy loss spectroscopy. The calculations indicate that the Fe atom in LaOFeP crystal shows a weak magnetic moment and does not form a long-range magnetic ordering. Band structure, Fermi surfaces and fluorine-doping effects are also analyzed based on the data of the density functional theory. The fine structures of the EELS data have been carefully examined in both the low loss energy region and the core losses region (O K, Fe L2,3, and La M4,5). A slight bump edge at 44 eV shows notable orientation-dependence: it can be observed in the low loss EELS spectra with q parallel to c, but becomes almost invisible in the q vertical to c spectra. Annealing experiments indicate that low oxygen pressure favors the appearance of superconductivity in LaOFeP, this fact is also confirmed by the changes of Fe L2,3 and O K excitation edges in the experimental EELS data.