Atomically thin van der Waals magnetic crystals are characterized by tunable magnetic properties related to their low dimensionality. While electrostatic gating has been used to tailor their magnetic response, chemical...

a Curie temperature close to the room temperature and strong out-of-plane anisotropy. [7][8][9][10] Moreover, the magnetic properties of FGT are tunable, as they can be modified either electrically, applying a gate voltage [11] and a large electrical current, [12] or through magnetic proximity effects. [13][14][15][16] In particular, when interfaced with antiferromagnetic layered materials, FGT displays an increased coercivity and exchange bias, [13][14][15][16] which are the prototypical manifestation of magnetic proximity [17][18][19] and are key elements in spintronic devices. [20] Another attractive approach to tune the properties of a magnetic surface is molecular functionalization. [21,22] The interfaces between magnetic materials and molecules, often named spinterfaces, [21,22] host hybrid states or magnetic interactions which lead to radical changes on the magnetic properties of both the molecular layer [23][24][25][26][27][28][29][30] and the magnetic material. [27][28][29][30][31][32][33] So far, the ferromagnetic layers used for investigating spinterface effects are typically films of 3d metals or oxides with dangling bonds on the surface, which result in nonideal interfaces with molecules. Moreover, until recently, the molecular side of a spinterface has been the main target of research due to its easily tunable electronic properties, [23][24][25][26][27][28][29] whereas the possibility of tailoring the magnetism of ferromagnetic materials has yet to be fully exploited.Layered magnetic materials are excellent candidates for developing a spinterface in view of their tunable magnetism and their single crystalline nature, which offer the possibility to form highly controllable interfaces with molecules [34,35] via the so-called van der Waals epitaxy. [36][37][38][39] Indeed, hybrid heterostructures based on atomically sharp 2D material/molecule interfaces have been widely used to tailor the optoelectronic and transport properties of nonmagnetic layered materials. [40][41][42][43][44][45] However, so far the possibility to tune the properties of a layered magnetic material through the magnetic interactions at a van der Waals spinterface has not yet been experimentally demonstrated.Here, we report on the emergence of spinterface effects between molecular films of Co-phthalocyanine (CoPc) and a few-nm-thick FGT flakes. The molecular layer induces a negative magnetic exchange bias in FGT, indicating that the The exfoliation of layered magnetic materials generates atomically thin flakes characterized by an ultrahigh surface sensitivity, which makes their magnetic properties tunable via external stimuli, such as electrostatic gating and proximity effects. Another powerful approach to engineer magnetic materials is molecular functionalization, generating hybrid interfaces with tailored magnetic interactions, called spinterfaces. However, spinterface effects have not yet been explored on layered magnetic materials. Here, the emergence of spinterface effects is demonstrated at the interface between flakes of the ...

When doped into a certain range of charge carrier concentrations, MoS 2 departs from its pristine semiconducting character to become a strongly correlated material characterized by exotic phenomena such as charge density waves or superconductivity. However, the required doping levels are typically achieved using ionic-liquid gating or air-sensitive alkali-ion intercalation, which are not compatible with standard device fabrication processes. Here, the emergence of superconductivity and a charge density wave phase in air-stable organic cation intercalated MoS 2 crystals are reported. By selecting two different molecular guests, it is shown that these correlated electronic phases depend dramatically on the intercalated cation, demonstrating the potential of organic ion intercalation to finely tune the properties of 2D materials. Moreover, it is found that a fully developed zeroresistance state is not reached in few-nm-thick flakes, indicating the presence of 3D superconductive paths that are severed by the mechanical exfoliation. This behavior is ascribed to an inhomogeneous charge carrier distribution, which is probed at the nanoscale using scanning near-field optical microscopy. The results establish organic-ion intercalated MoS 2 as a platform to study the emergence and modulation of correlated electronic phases.

Intercalation is the insertion of guest species between the planes of a host van der Waals layered crystal. The process is accompanied by a significant change of the charge carrier density and by the expansion of the interlayer distance, overall leading to a modification of the electronic band structure of the layered material. This perspective focuses on the possibilities offered by the intercalation of organic ions toward finely tuning the physical properties of van der Waals materials, in particular their magnetism and superconductivity. How the intercalation of organic ions offers several advantages over conventional guest species such as alkali metals is highlighted, since a careful choice of the molecular intercalant opens the possibility to tailor the interlayer distance and the charge carrier density. Moreover, specific properties of the molecular guest can be transferred to the host material, as recently demonstrated by the intercalation of thermo‐responsive and chiral molecules. It is anticipated that other functional organic ions can be incorporated in van der Waals materials to provide additional optical and magnetic capabilities, with the potential to enable an optical control of magnetism and superconductivity.

Atomically thin van der Waals magnetic crystals are characterized by tunable magnetic properties related to their low dimensionality. While electrostatic gating has been used to tailor their magnetic response, chemical approaches like intercalation remain largely unexplored. Here, we demonstrate the manipulation of the magnetism in the van der Waals antiferromagnet NiPS3 through the intercalation of different organic cations, inserted using an engineered two-step process. First, the electrochemical intercalation of tetrabutylammonium cations (TBA+) results in a ferrimagnetic hybrid compound displaying a transition temperature of 78 K, and characterized by a hysteretic behavior with finite remanence and coercivity. Then, TBA+ cations are replaced by cobaltocenium via an ion-exchange process, yielding a ferrimagnetic phase with higher transition temperature (98 K) and higher remanent magnetization. Importantly, we demonstrate that the intercalation and cation exchange processes can be carried out in bulk crystals and few-layer flakes, opening the way to the integration of intercalated magnetic materials in devices.