Two-dimensional (2D) spintronic devices based on van der Waals (vdW) heterostructures have potential applications in magnetic sensing and data storage. Here, we report vdW heterostructures fabricated by stacking an exfoliated ultrathin black phosphorus (BP) or violet phosphorus (VP) spacer between two exfoliated ferromagnetic Fe₃GeTe₂ (FGT) electrodes. The devices achieve high magnetoresistance (MR) ratios of 40.4% and 31.5% for the FGT/BP/FGT and FGT/VP/FGT heterostructures at low temperature, respectively. The magnitude of MR can be tuned by bias current and spacer thickness. Moreover, magnetotransport measurements confirm robust spin valve effect, showing angular-independent MR in FGT-based heterostructures. Our work opens a new avenue for the application of monoelemental phosphorus as spacer in novel spintronic devices.