  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.
