1B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine 47 Lenin Ave., Kharkov 61103, Ukraine
E-mail: naidyuk@ilt.kharkov.ua
2Kamerlingh Onnes Laboratory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
Received December 21, 2012
Abstract
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.
