# Magnetism Induced by Azanide and Ammonia Adsorption in Defective Molybdenum Disulfide and Diselenide: A First-Principles Study

## TL;DR

This study shows that adding ammonia or azanide to defective molybdenum disulfide and diselenide can create magnetism, which could be useful for spintronic devices.

## Contribution

The novel finding is that NH2 and NH3 adsorption induces magnetism in defective Mo-based dichalcogenides.

## Key findings

- Pristine chalcogen vacancies do not generate magnetism, but NH2 and NH3 adsorption creates localized magnetic moments.
- NH3 dissociation on MoSe2 produces a net magnetic moment of 2.0 μB.
- W-based dichalcogenides show no magnetic response under similar conditions.

## Abstract

Two-dimensional (2D) transition metal dichalcogenides
(TMDs) have
attracted considerable attention due to their tunable structural,
electronic, and spin-related properties, particularly in the presence
of point defects and molecular adsorbates. Motivated by these aspects,
we have investigated using first-principles methods, the magnetic
properties induced by azanide (NH2) and ammonia (NH3) adsorption on defective monolayers of molybdenum disulfide
(MoS2) and molybdenum diselenide (MoSe2). Spin-polarized
density functional theory (DFT) at the generalized gradient approximation
(GGA) level, using the Perdew–Burke–Ernzerhof (PBE)
functional, was employed to investigate the impact of mono- and divacancies
on the local spin environment and the role of molecular adsorption
in modifying magnetic behavior. The results show that pristine chalcogen
vacancies do not generate magnetism, whereas the adsorption of NH2 and NH3 creates localized magnetic moments in
Mo-based dichalcogenides. A notable case occurs for MoSe2, where NH3 dissociation into NH2 and H fragments
on the same side of the surface produces a net magnetic moment of
2.0 μB. Tests performed on W-based dichalcogenides
under equivalent conditions showed no magnetic response and are reported
here only for comparison. These findings demonstrate that molecular
adsorption combined with defect engineering can be a practical approach
to tune magnetism in 2D materials, with potential relevance for spintronic
and sensing applications.