The integration of ferromagnetic and semiconducting properties in a single two-dimensional (2D) material has been recognized as a fertile ground for fundamental science as well as for practical applications in information processing and storage. CrI 3 monolayer has recently drawn much attention due to its 2D long-range ferromagnetic (FM) order. However, its Curie temperature (T C ) is too low (∼45 K) for practical spintronic applications. Here, we show that the in-plane FM coupling of CrI 3 can be remarkably enhanced by constructing a 2D heterostructure where CrI 3 monolayer is supported on a nonmagnetic normal semiconductor/insulator substrate. Choosing MoTe 2 monolayer as a substrate, we find that the CrI 3 /MoTe 2 2D heterostructure is an intrinsic semiconducting ferromagnet with T C of ∼60 K. The T C can be further increased to ∼85 K by applying an out-of-plane pressure of ∼4.2 GPa. The doubling of the T C in this 2D heterostructure comes from the introduction of extra spin superexchange (Cr−Te−Cr) paths. Our findings provide a promising pathway to improve ferromagnetism in 2D semiconductors, which can stimulate further theoretical and experimental interest.
Two-dimensional (2D) ferromagnetic (FM) semiconductors with a direct electric band gap have recently drawn much attention due to their promising potential for spintronic and magneto-optical applications.
Contact electrification (triboelectrification) (CE) is a universal phenomenon in ambient environment and has been recorded for more than 2600 years. Nonetheless, the intrinsic mechanism of CE still remains controversial. Herein, based on first-principles theory, the underlying mechanism in CE is systematically investigated between metallic MXenes and semiconductive MoS 2 . The results show that the work functions of contacting materials dominate the direction of electron transfer during CE process. That is, the electron will be transferred from the material with low work function to the one with high work function. The theoretical prediction is verified experimentally through investigating triboelectric probes based on MXenes and MoS 2 nanomaterials. Additionally, it is noted that the interfacial potential barrier and the work function difference together modulate the amount of transferred electron. Electron transfer mainly occurs in the repulsive forces region where the interaction distance between the two materials is shorter than the normal bonding length. The quantum calculation results agree well with the Wang transition theory. Furthermore, it is also noticed that, due to the wave-particle duality of electron, electron transfer will obviously occur at the attractive force region when the two contacting materials exhibit a larger work function difference.
Electrical
control of magnetic order in van der Waals (vdW) two-dimensional
(2D) systems is appealing for high-efficiency and low-dissipation
nanospintronic devices. For realistic applications, a vdW 2D material
with ferromagnetic (FM) and ferroelectric (FE) orders coexisting and
strongly coupling at room temperature is urgently needed. Here we
present a potential candidate for nonvolatile electric-field control
of magnetic orders at room temperature. Using first-principles calculations,
we predict the coexistence of room-temperature FM and FE orders in
a 2D transition metal carbide, where the spatial distribution of magnetic
moments strongly couples with the orientation of out-of-plane electric
polarization. Furthermore, an electric-field switching between interfacial
FM and ferrimagnetic orders is realizable through constructing a multiferroic
vdW heterostructure based on this material. These findings make a
significant step toward realizing room-temperature multiferroicity
and strong magnetoelectric coupling in 2D materials.
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