Magnon-assisted tunnelling in van der Waals heterostructures based on CrBr3

Abstract

The growing family of two-dimensional (2D) materials 1-3 can be used to assemble van der Waals heterostructures with a wide range of properties 4-6 . Of particular interest are tunnelling heterostructures 7-9 , which have been used to study the electronic states both in the tunnelling barrier and in the emitter and collector contacts 10,11 . Recently, 2D ferromagnets have been studied theoretically 12-15 and experimentally 16-18 . Here we investigate electron tunnelling through a thin (2-6 layers) ferromagnetic CrBr 3 barrier. For devices with non-magnetic barriers, conservation of momentum can be relaxed by phonon-assisted tunnelling 8,19-21 or by tunnelling through localised states 8,21,22 . In the case of our ferromagnetic barrier the dominant tunnelling mechanisms are the emission of magnons 18 at low temperatures or scattering of electrons on localised magnetic excitations above the Curie temperature. Magnetoresistance in the graphene electrodes further suggests induced spin-orbit coupling and proximity exchange via the ferromagnetic barrier. Tunnelling with magnon emission offers the possibility of spin-injection, as has been previously demonstrated with other ferromagnetic barriers 23,24 . S1. Device fabrication S2. Temperature dependence of differential dI/dV b conductance on magnetic field for devices with different thickness of CrBr 3 S3. Quantum capacitance of Gr/CrBr 3 /Gr devices S4. Calculation of magnon density of states S5. Scattering rates

Orbitally-resolved ferromagnetism of monolayer CrI3

“…Magnetic anisotropy ensures a gap in the spin-wave spectrum, resulting in a finite Curie temperature, as it immediately follows from Eqs. (5) and (4). To estimate the Curie temperature in CrI 3 , we consider two magnetic sublattices and solve the system of equations given by Eq.…”

“…Recent discovery of ferromagnetism in two-dimensional (2D) materials has triggered enormous interest to these materials from the research community [1][2][3][4][5][6]. Apart from being fundamentally interesting object in the context of the Mermin-Wagner theorem, which forbids magnetic ordering in 2D at any nonzero temperature for the case of isotropic Heisenberg or easy-plane-anisotropic magnets [7], 2D magnets are especially promising for applications, such as spintronics, quantum computing and energy-efficient electronics [8][9][10][11].…”

On the Ferromagnetism and Band Tailoring of CrI3Single Layer

“…This makes the I 5p electron more polarized, for example, the spin magnetic moment of I 2 becomes twice as large as before (Table ). However, this is different from most doping or defect cases where it is the transition metal ions dominant in the neighborhood of E F as the conducting electrons . In other words, with or without vacancy the Cr 3d states can be survived, but I 5d states become across the E F as a result of the “hole doping” effect.…”

Spin-dependent Schottky barriers and vacancy-induced spin-selective ohmic contacts in magnetic vdW heterostructures

“…This result indicates graphene is a charge-donating substrate for CrX3, and it is expectable as the calculated work function of graphene (4.28 eV) is smaller than the electron affinity of CrX3 (5. 38,4.73, and 4.69 eV for CrCl3, CrBr3 and CrI3, respectively). This is different to the MoS2/Gr heterostructure, in which the charge transfers from MoS2 to graphene.…”

“…Among various 2D electrode candidates, graphene is one of most widely used material due to its high-performance and low-cost. For example, the graphene has been used in CrX3based spin device including the multiple-spin-filter MTJs, [4,[9][10][11][12][13][14][15]] and very high large tunneling MR values up to 19 000% has been reported. Furthermore, as vacancy is inevitable in 2D materials, which is known to affect the physical properties of host remarkably.…”