Magnetostatic and exchange coupling in the magnetization reversal of trilayer nanodots

Abstract

We present an experimental investigation of the magnetization reversal process in Ni80Fe20(10 nm)/Cu/Co(10 nm) sub-micrometric circular discs for two different thicknesses of the Cu spacer (1 and 10 nm). Magnetic hysteresis loops were measured by the longitudinal magneto-optical Kerr effect and by resonant scattering of polarized soft x-ray. The results for the 10 nm thick Cu interlayer show a complex magnetization reversal process determined by the interplay between the interlayer dipolar interaction and the different reversal nucleation fields in the two layers. It is worth noting that, during the reversal process, the magnetization of the two layers remains in a nearly single domain state due to the dipolar coupling. These findings are confirmed by three-dimensional micromagnetic simulations. In contrast, when the Cu spacer is 1 nm thick both measurements and simulations show that the reversal is accomplished via the formation of a vortex state in both discs due to the presence of a ferromagnetic exchange coupling that competes with the dipolar interaction.

Quantized spin-wave modes in magnetic tunnel junction nanopillars

“…4 The eigenexcitations of a multi-layer dot differ in general significantly from those of an ensemble of isolated magnetic dots due to the interlayer interactions between the magnetic layers in the stack: mutual dipolar coupling and -for sufficiently thin metallic spacer layers -interlayer exchange coupling. 10 Eigenexcitations of nanopillar structures have been the subject of very few studies so far. Thermal spin waves have been investigated systematically only in pseudo-spin-valves [11][12][13] of circular and elliptical shape (smallest dimension 200 nm) consisting of two magnetic layers of 10 nm thickness separated by a 10 nm thick spacer layer, i.e.…”

Ellipsometric Selective Sensitivity to Magnetic Nanostructures

“…(5) on the parameters ∆α and k. We see that we can obtain reasonable small condition number if parameter k is not too different from 1 and vectors Φ 1 and Φ 2 are not collinear. Then we can separate magnetization contributions of one material from two different depths [5,6] but also magnetization contributions from two different materials [2,7,8].…”

Selective sensitivity of ellipsometry to magnetic nanostructures

“…Selective sensitivity of the complex MO effect was obtained also for nanostructures consisting of different magnetic materials [11][12][13]. Material selective sensitivity of polar magnetooptic Kerr effect was described and experimentally demonstrated in NiFe/Au/Co/Au multilayers [11].…”

“…Moreover, the magneto-optic Kerr effects enable us to separate magnetic contributions from different depth [6][7][8][9][10] and from different materials [11,12] in multilayer systems and self-organized nanostructures [13].…”