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

• We investigate the interstitials to induce d0 magnetism in α-PbO crystal lattice.
• The oxygen interstitial is a perspective candidate due to its low formation energy.
• The on-site unpaired electron is acquired in the charged state.
• The oxygen interstitial is the negative U defect.
• The spin coupling between defects is found to be stable only at low temperature.

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=0.123 eV) 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.