Nitrogen Vacancy and Magnetic Property in Cu-Doped AlN From First-Principles Calculations

The effects on the ferromagnetism of a nitrogen defect in Cu-doped AlN with a Cu concentration of 2.77–8.33% have been investigated by first-principles. For Al
$_{0.9723}$
Cu
$_{0.0277}$
N, a global magnetic moment of 1.46
$\mu_{\rm B}$
/cell, with a localized magnetic moment of 0.75
$\mu_{\rm B}$
/Cu is found. The formation of Cu-Cu in AlN with the N vacancy
$({\rm V}_{\rm N})$
is more energetically favorable than that without the
${\rm V}_{\rm N}$
. Hence, the
${\rm Cu}+{\rm V}_{\rm N}$
state is produced easily. The Cu magnetic moment of Cu-Cu pair becomes very low by the weak 3d-3d spin coupling due to the spin-exchange interaction between Cu-3d and N defect states.