Magnetic and structural characteristics of exchange biasing systems based on NiMn antiferromagnetic films

NiMn/FeNi exchange biasing systems–magnetic and structural characteristics after short annealing close to the phase transition point of the AFM layer

“…3d, the estimated minimal mean crystallite grain size of the dominating NiMn phase is L ð1 1 1ÞFCCNiMn E35 nm for T an p325 C and L ð1 1 1ÞFCT Ã NiMn E45 nm for T an X350 C. This difference in the L ð1 1 1Þ values of the two NiMn phases is related most probably both to some stress relaxation and to some further columnar grain growth during the annealing procedure due to the inertness of the cooling procedure. According to the TEM results on similar samples shown in our work [6], the diameter of the columnar grains is about 20 nm and undergoes only a small change.…”

“…The details of the magnetron sputtering deposition procedure are described in Ref. [6]. The deposition parameters of the NiMn films investigated in this work are v dep1 ¼ 12:5 nm/min (v dep2 ¼ 28 nm/min) and p Ar1 ¼ 7:5 Â 10 À4 mbar (p Ar2 ¼ 1 Â 10 À3 mbar).…”

“…The chemical composition of the as-deposited and the annealed samples was determined by glow discharge optical spectrometry analysis [6,14] using a Leco SPD-750 surface depth profile emission spectrometer and an Ni 50 Mn 50 reference probe. The Ni concentration found in the films is between 48 and 52 at% and corresponds to the phase diagram region where formation of a stoichiometric Ni 50 Mn 50 phase is expected [15].…”

“…Especially interesting objects for investigation of the above correlation are the bi-layer systems based on NiMn AFM film. This alloy thin film material has shown both high EB field and high blocking temperature [3][4][5][6] and it is representative of a class of AFM materials having the same chemically ordered CuAu-type I face centered tetragonal (FCT) structure in the AFM state [7].…”

“…For example, in Ref. [6] we reported on the formation of NiMn alloy films with different ratios of the equilibrium FCT and the non-equilibrium FCC phases as a function of the sputtering pressure and the deposition rate. In some of the investigated films deposited at lower p Ar we found almost 100% of the non-equilibrium high-temperature FCC NiMn phase which remains stable when short-time annealing at T an o325 C has been performed.…”