Spin-Valve Effect in Junctions with a Single Ferromagnet

Spin valves are essential components in spintronic memory devices whose conductance is modulated by controlling spin-polarized electron tunnelling through the alignment of the magnetization in ferromagnetic elements. Whereas conventional spin valves unavoidably require at least two ferromagnetic elements, here we demonstrate a van der Waals spin valve based on a tunnel junction that comprises only one such ferromagnetic layer. Our devices combine an Fe₃GeTe₂ electrode acting as a spin injector together with a paramagnetic tunnel barrier, formed by a CrBr₃ multilayer operated above its Curie temperature. We show that these devices exhibit a conductance modulation with values comparable to those of conventional spin valves. A quantitative analysis of the magnetoconductance that accounts for the field-induced magnetization of CrBr₃, including the effect of exchange interaction, confirms that the spin valve effect originates from the paramagnetic response of the barrier, in the absence of spontaneous magnetization in CrBr₃.