Magnetization process inSm40Fe60(88nm)/

Abstract

The magnetization reversal in a sputtered Sm 40 Fe 60 (88 nm)/Ni 80 Fe 20 (62 nm) hard/soft bilayer with induced uniaxial anisotropy was investigated by Kerr microscopy and magnetometry. In the reversible regime of the hysteresis loop a twisting of magnetization across the thickness of the soft magnetic film could be derived. The hard layer reverses by the nucleation and growth of regular domains. They are separated from the nonswitched areas by tilted domain walls, the angle of which can be predicted by considering the net magnetic moments of the bilayer system.

Noncollinear Fe spin structure in (Sm-Co)/Fe exchange-spring bilayers: Layer-resolved57Fe Mössbauer spectroscopy and electronic structure calculations

“…For the latter case, lower external fields for switching are required for thicker Fe slabs. Similar effects were found by phenomenological theories [19,22,23,32,34,35[. Our results indicate that, despite the huge internal interfacial exchange-anisotropy field H int of the order of tens of Tesla, the formation of the spin spiral in our 100 ML Fe slab for applied external fields of less than 1 T gives rise to a rotation of the interfacial Fe moment, which could not take place if the soft phase is formed by very few Fe layers.…”

“…7(c) Fe and natural Fe alone, since the theo retical upper limit of R min in this case is equal to R min for the whole Fe slab ('all'), which is equal to 0.8 -0.9 according to Fig. 7 (c Fluctuations in the interface coupling were conceived earlier in order to interpret the observed strongly reduced domain nucleation field at irreversible switching of SmFe/NiFe hard/soft bilayers as compared to the nucleation field of a single SmFe film [19]. Our present findings support such an interpretation.…”

“…It is known that in certain cases [19] a difference in the measurement time scale can lead to a difference in the observed values of the irreversible switching field, Hirr, of the hard magnetic layer during magnetization reversal ("magnetic after-effect" or "magnetic viscosity"). For the Mössbauer measurements, it took about 24 hours per spectrum, whereas it took about one second per data point in the AGM measurements.…”

“…In Fig. 7 (b), the R 23 dependence of the interface (1-10 ML) and near-interface (15)(16)(17)(18)(19)(20)(21)(22)(23)(24) probe layers still exhibits a monotonic drop, but one can expect formation of a R 23 minimum even in the case of H int = ∞ for severe 57 Fe -56 Fe intermixing.…”

“…The loop shapes observed in Fig. 2 display a double step and are typical for layered exchange-spring magnetic systems [19,[22][23][24]. Upon decreasing the field from positive saturation, a sharp drop of the magnetization occurs at the so-called nucleation field μ 0 H n (also called exchange field μ 0 H ex in Ref.…”