Large exchange bias in polycrystalline MnN/CoFe bilayers at room temperature

We report on the new polycrystalline exchange bias system MnN/CoFe, which shows exchange bias of up to 1800 Oe at room temperature with a coercive field around 600 Oe. The room-temperature values of the interfacial exchange energy and the effective uniaxial anisotropy are estimated to be Jeff=0.410.28em0exmJ/m² and Keff=370.28em0exkJ/m³. The thermal stability was found to be tunable by controlling the nitrogen content of MnN. The maximum blocking temperature exceeds 3250.16em0ex^∘C, however the median blocking temperature in the limit of thick MnN is 1600.16em0ex^∘C. Good oxidation stability through self-passivation was observed, enabling the use of MnN in lithographically defined microstructures. As a proof of principle we demonstrate a simple giant magnetoresistance stack exchange biased with MnN, which shows clear separation between parallel and antiparallel magnetic states. These properties come along with a surprisingly simple manufacturing process for the MnN films.