The O interstitials in α-PbO crystal lattice to induce the magnetic properties

Abstract

We used the first principles methods to study the properties of the O self-interstitial defect in an α-PbO crystal lattice in order to reveal its potential to host the unpaired electrons. The mechanism of bonding of the interstitial defects in the α-PbO compound (Berashevich and Reznik, 2013) is unique as at proper occupation of their p-orbital they can act as the magnetic centers. The O interstitial is considered here due to its low formation energy as the high defect solubility is required for the magnetic percolation to manifest between the localized electrons. Although in its zero charge state the O interstitial hosts no unpaired electron, it can be induced upon defect ionization to the negatively charged state (Oi(1−)). The spin-polarization energy of the Oi(1−) state is established to be quite high (EM=0.123eV) indicating a stability of the spin state. As two Oi(1−) defects interact, their unpaired electrons are found to order antiferromagnetically. However, the Oi(1−) defect is found to be the ”negative U defect” and in such, two interacting defects are unstable with respect to dissociation into the Oi(2−) and Oi(0) states possessing no unpaired electrons. It imposes the low temperature limit on the magnetic interactions between the Oi(1−) defects.