2 research outputs found
Electronic band structure changes across the antiferromagnetic phase transition of exfoliated MnPS probed by -ARPES
Exfoliated magnetic 2D materials enable versatile tuning of magnetization,
e.g., by gating or providing proximity-induced exchange interaction. However,
their electronic band structure after exfoliation has not been probed, most
likely due to their photochemical sensitivity. Here, we provide micron-scale
angle-resolved photoelectron spectroscopy of the exfoliated intralayer
antiferromagnet MnPS above and below the N\'{e}el temperature down to one
monolayer. The favorable comparison with density functional theory calculations
enables to identify the orbital character of the observed bands. Consistently,
we find pronounced changes across the N\'{e}el temperature for bands that
consist of Mn 3d and 3p levels of adjacent S atoms. The deduced orbital mixture
indicates that the superexchange is relevant for the magnetic interaction.
There are only minor changes between monolayer and thicker films demonstrating
the predominant 2D character of MnPS. The novel access is transferable to
other MPX materials (M: transition metal, P: phosphorus, X: chalcogenide)
providing a multitude of antiferromagnetic arrangements.Comment: 26 pages, 17 figure
Limited ferromagnetic interactions in monolayers of MPS (M=Mn, Ni)
We present a systematic study of the electronic and magnetic properties of
two-dimensional ordered alloys, consisting of two representative hosts
(MnPS and NiPS) of transition metal phosphorus trichalcogenides doped
with elements. For both hosts our DFT+U calculations are able to
qualitatively reproduce the ratios and signs of all experimentally observed
magnetic couplings. The relative strength of all antiferromagnetic exchange
couplings, both in MnPS as well as in NiPS, can successfully be
explained using an effective direct exchange model: they reveal that the
third-neighbor exchange dominates in NiPS due to the filling of the
subshell, whereas for MnPS the first neighbor exchange is
prevailed owing to the presence of the magnetism. On the other hand,
the nearest neighbor ferromagnetic coupling in NiPS can only be explained
using a more complex superexchange model and is (also) largely triggered by the
absence of the magnetism. For the doped systems, the DFT+U
calculations revealed that magnetic impurities do not affect the magnetic
ordering observed in the pure phases and thus in general in these systems
ferromagnetism may not be easily induced by such a kind of elemental doping.
However, unlike for the hosts, the first and second (dopant-host) exchange
couplings are of similar order of magnitude. This leads to frustration in case
of antiferromagnetic coupling and may be one of the reasons of the observed
lower magnetic ordering temperature of the doped systems.Comment: 15 pages, 8 figures, 3 table