1B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Lenin Ave., Kharkov 61103, Ukraine
2Kamerlingh Onnes Laboratory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
Received December 21, 2012
We present a study of the influence of an external magnetic field H and an electric current I on the spin-valve (SV) effect in point contact between a ferromagnetic thin film (F) and a sharp tip of a nonmagnetic metal (N). To explain our observations, we propose a model of a local surface SV which is formed in such a N/F contact. In this model, a ferromagnetic cluster at the N/F interface plays the role of the free layer in this SV. This cluster exhibits a larger coercive field than the bulk of the ferromagnetic film, presumably due to its nanoscale nature. Finally, we construct a magnetic state diagram of the surface SV as a function of I and H.
PACS: 72.25.–b Spin polarized transport; PACS: 73.40.Jn Metal-to-metal contacts; PACS: 75.75.+a Magnetic properties of nanostructures; PACS: 85.75.–d Magnetoelectronics; spintronics.
Key words: point contacts, spin valve, spin transfer torque, magnetic phase diagram.