We propose a spin valve based on a blue-phosphorus monolayer sandwiched between two half-metallic two-dimensional Cr N layers. We use density-functional theory combined with Boltzmann transport theory to investigate both the structural and the magnetic stability of the Cr N / P / Cr N heterostructure and to study its spin-dependent transport properties. Among the different possible layer stackings considered, only one is shown to be thermodynamically stable, corresponding to the AA stacking. In this geometry, the critical temperature of magnetic ordering is estimated to be around 150 K. The electronic structure of Cr N / P / Cr N is strongly dependent on the mutual orientation of the magnetic moments in individual Cr N layers. If the alignment is parallel, only one spin channel predominantly contributes to the electronic bands in the vicinity of the Fermi energy. In the case of an antiparallel alignment, both spin channels contribute to the electronic states. The alteration of magnetic moments affects electronic transport, causing magnetoresistance of up to 12% at moderate dopings.

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