Gate‐Controlled Magnetotransport and Electrostatic Modulation of Magnetism in 2D Magnetic Semiconductor CrPS₄

Abstract

Using field‐effect transistors (FETs) to explore atomically thin magnetic semiconductors with transport measurements is difficult, because the very narrow bands of most 2D magnetic semiconductors cause carrier localization, preventing transistor operation. Here, it is shown that exfoliated layers of CrPS4—a 2D layered antiferromagnetic semiconductor whose bandwidth approaches 1 eV—allow the realization of FETs that operate properly down to cryogenic temperature. Using these devices, conductance measurements as a function of temperature and magnetic field are performed to determine the full magnetic phase diagram, which includes a spin‐flop and a spin‐flip phase. The magnetoconductance, which depends strongly on gate voltage, is determined. reaching values as high as 5000% near the threshold for electron conduction. The gate voltage also allows the magnetic states to be tuned, despite the relatively large thickness of the CrPS4 multilayers employed in the study. The results show the need to employ 2D magnetic semiconductors with sufficiently large bandwidth to realize properly functioning transistors, and identify a candidate material to realize a fully gate‐tunable half‐metallic conductor.

Magnetism-Induced Band-Edge Shift as the Mechanism for Magnetoconductance in CrPS4 Transistors

“…The overall experimental phenomenology of the magnetotransport response of CrPS 4 transistors has been very recently reported in ref . That work presents all key experimental observations but does not discuss the physical mechanisms responsible for the observed magnetotransport, which remains to be determined.…”

“…27−29 In devices based on multilayers of the most recently reported compound, the van der Waals antiferromagnetic semiconductor CrPS 4 (see Figure 1a,b), the magnetoconductance has been found to be very large (reaching up to ≈10000%) and strongly dependent on the gate voltage (as we reproduce in Figure 1c,d for convenience). 29 It has been clearly established that the measured magnetoconductance is determined by how the magnetic state of CrPS 4 evolves when a magnetic field is applied, but its precise microscopic origin could not be identified.…”

“…The effect of the narrow bandwidth also has a pronounced impact on the transport properties, which is why the realization of field-effect transistors enabling the controlled and systematic investigation of transport as a function of electron density has proven difficult on 2D magnetic semiconductors. − ,, Only recently, the first materials have been identified with a bandwidth of 1 eV or larger, − allowing transistors to operate well below the magnetic critical temperature and enabling systematic studies of magnetotransport. − In devices based on multilayers of the most recently reported compound, the van der Waals antiferromagnetic semiconductor CrPS 4 (see Figure a,b), the magnetoconductance has been found to be very large (reaching up to ≈10000%) and strongly dependent on the gate voltage (as we reproduce in Figure c,d for convenience) . It has been clearly established that the measured magnetoconductance is determined by how the magnetic state of CrPS 4 evolves when a magnetic field is applied, but its precise microscopic origin could not be identified.…”

“…(a) Crystal structure of layered CrPS 4 ; the blue, yellow, and orange spheres represent Cr, S, and P atoms, respectively. CrPS 4 has an antiferromagnetic ground state (A-type) formed by individual layers uniformly magnetized in the out-of-plane direction ( T N ≈ 35 K). − Panels (b)–(d) summarize the key features of CrPS 4 -transistors reported in ref . (b) Transfer curves ( G □ -vs- V G ) of a 10 nm thick CrPS 4 FET device at 200 and 2 K. The inset shows the device schematics.…”

“…(b) Transfer curves ( G □ -vs- V G ) of a 10 nm thick CrPS 4 FET device at 200 and 2 K. The inset shows the device schematics. A hBN-encapsulated CrPS 4 multilayerwith thickness ranging from 6 to 10 nm in different devicesis contacted by graphene stripes and the gate voltage V G is applied across a 285 nm SiO 2 insulating layer (for experimental details about the precise configuration of the device and its fabrication see ref ). (c) Magnetoconductance ( δ G = G ( μ 0 H ) − G ( 0 ⁡ T ) G ( 0 ⁡ T ) ) measured at T = 2 K for fixed V G values in the 50–100 V range, in 10 V steps.…”