A magnetoresistive sensor based on the spin accumulation effect has an in-stack biasing structure with a ferromagnetic biasing layer that is magnetically-coupled orthogonally with the sensor free ferromagnetic layer across a spacer layer. The sensor has an electrically conductive strip with a first tunnel barrier and a free ferromagnetic layer on the front or sensing end of the strip and second tunnel barrier and a fixed ferromagnetic layer on the back end of the strip. A magnetically-coupling spacer layer is formed on the free layer and the ferromagnetic biasing layer is formed on the spacer layer. The magnetically-coupling layer induces direct orthogonal magnetic coupling between the in-plane magnetization directions of the biasing layer and the free layer.