Magnetization dependent tunneling conductance of ferromagnetic barriers

Abstract

Recent experiments on van der Waals antiferrmagnets such as CrI3, CrCl3 and MnPS3 have shown that using atomically thin layers as tunnel barriers and measuring the temperature ($T$) and magnetic field ($H$) dependence of the conductance allows their magnetic phase diagram to be mapped. In contrast, barriers made of CrBr3 -- the sole van der Waals ferromagnet investigated in this way -- were found to exhibit small and featureless magnetoconductance, seemingly carrying little information about magnetism. Here we show that -- despite these early results -- the conductance of CrBr3 tunnel barriers does provide detailed information about the magnetic state of atomically thin CrBr3 crystals for $T$ both above and below the Curie temperature ($T_C = 32$ K). Our analysis establishes that the tunneling conductance depends on $H$ and $T$ exclusively through the magnetization $M(H,T)$, over the entire temperature range investigated (2-50 K). The phenomenon is reproduced in detail by the spin-dependent Fowler-Nordheim model for tunneling, and is a direct manifestation of the spin splitting of the CrBr3 conduction band. These findings demonstrate that the investigation of magnetism by tunneling conductance measurements is not limited to antiferromagnets, but can also be applied to ferromagnetic materials.