  The structural, magnetic, vibrational and electronic properties of single
layer aluminum oxide (AlO2) are investigated by performing state-of-the-art
first-principles calculations. Total energy optimization and phonon
calculations reveal that aluminum oxide forms a distorted octahedral structure
(1T'-AlO2) in its single layer limit. It is also shown that surfaces of
1T'-AlO2 display magnetic behavior originating from the O atoms. While the
ferromagnetic (FM) state is the most favorable magnetic order for 1T'-AlO2,
transformation to a dynamically stable antiferromagnetic (AFM) state upon a
slight distortion in the crystal structure is also possible. It is also shown
that Raman activities (350-400 cm^-1) obtained from the vibrational spectrum
can be utilized to distinguish the possible magnetic phases of the crystal
structure. Electronically, both FM and the AFM phases are semiconductors with
an indirect band gap and they can form a type-III vdW heterojunction with
graphene-like ultra-thin materials. Moreover, it is predicted that presence of
oxygen defects that inevitably occur during synthesis and production do not
alter the magnetic state, even at high vacancy density. Apparently, ultra-thin
1T'-AlO2 with its stable crystal structure, semiconducting nature and robust
magnetic state is a quite promising material for nanoscale device applications.
