Magnetic Properties of the Iron-Doped LiBa12(BO3)7F4 Fluoroborate (LBBF)

Abstract

Magnetic properties of iron-doped LBBF samples are quite complex. Along with the paramagnetic component, magnetic susceptibility contains also the ferromagnetic contribution. The ratio of these components depends nonlinearly on the concentration of introduced iron, and so also do the effective magnetic moment of the iron ion and the Weiss constant that are determined by analysing the paramagnetic component of magnetic susceptibility. Changes in the magnetic properties of the studied compounds are accompanied by changes in the structure of 2p lines of X-ray photoelectron spectra of iron, whereas lines of other elements maintain their structure and energy positions. The main reasons of changes in magnetic properties with increasing iron concentration include changes in the space group in which the compounds crystallize, changes in the oxidation state of iron from 3+ to 2+, formation of superparamagnetic clusters, and isolation of an impurity phase for iron concentrations higher than 0.3 wt.%. Compounds with iron concentrations below 0.3 wt.%, crystallizing in the Pbam space group, exhibit more interesting properties. They are characterized by a larger ferromagnetic contribution and a larger effective magnetic moment of the paramagnetic center compared with the samples containing from 0.3 wt.% to 1 wt.% of iron and crystallizing in the P4₂bc space group, similarly to the initial LBBF.