GMR Spin Valve with alternating in-plane and out-of-plane magnetic anisotropy
|Bogdan Szymański , Feliks Stobiecki , Maciej Urbaniak|
Polish Academy of Sciences, Institute of Molecular Physics, Mariana Smoluchowskiego 17, Poznań 60-179, Poland
In this paper a new type of spin valve (SV) structure is proposed. It consists of ferromagnetic layers, with in-plane (F1) and out-of-plane (F2) anisotropy, separated by nonmagnetic spacer (S). When the magnetic field H is applied perpendicularly to the surface of the (F1/S/F2/S) SV it stabilizes the magnetization direction of the layers with perpendicular anisotropy and forces a rotation of the magnetization direction of the layers with easy plane anisotropy. This situation is reversed for the magnetic field applied parallel to the film surface. The magnetization reversal results in the giant magnetoresistance (GMR) characterized by the linear R(H) dependence in a wide range of magnetic field H.
To realize the idea of the SV we have chosen thin Co layers sandwiched between Au as layers with perpendicular anisotropy (F2). Our measurements proved that Co layers possess a perpendicular anisotropy for 0.4<tCo<1.5 nm and in-plane anisotropy for tCo>1.8 nm. We have found that for Co thickness 0.6<tCo<0.8 nm the effective perpendicular anisotropy is relatively strong. It does not change appreciably in the temperature range from 100 to 423K and is resistant to a low temperature annealing, i.e., Tanneal<450K. As ferromagnetic layers with in-plane anisotropy (F1) we have applied Ni-Fe (tNiFe=2 nm) or Co with thickness tCo>1.8 nm. For both types of structures, i.e., [NiFe1/Au/Co2/Au]N and [Co1/Au/Co2/Au]N multilayers (N is number of repetition), deposited by the magnetron sputtering, the GMR effect of up to 8% at RT was observed. Moreover, due to the considerable simplification, the Co1/Au/Co2/Au structures are preferred for applications (only two materials are required).
Presentation: poster at E-MRS Fall Meeting 2005, Symposium D, by Bogdan Szymański
See On-line Journal of E-MRS Fall Meeting 2005
Submitted: 2005-05-25 09:38 Revised: 2009-06-07 00:44