Magnetization reversal in Py/Gd heterostructures

Abstract

Using a combination of magnetometry and magnetotransport techniques, we studied temperature and magnetic field behavior of magnetization in Py/Gd heterostructures. It was shown quantitatively that proximity with Py enhances magnetic order ofGd. Micromagnetic simulations demonstrate that a spin-flop transition observed in a Py/Gd bilayer is due to exchange-spring rotation of magnetization in the Gd layer. Transport measurements show that the magnetoresistance of a [Py(2 nm)/Gd(2 nm)]25 multilayer changes sign at the compensation temperature and below 20 K. The positive magnetoresistance above the compensation temperature can be attributed to an in-plane domain-wall, which appears because of the structural inhomogeneity of the film over its thickness. By measuring the angular dependence of resistance we are able to determine the angle between magnetizations in the multilayer and the magnetic field at different temperatures. The measurement reveals that due to a change of the chemical thickness profile, a non-collinear magnetization configuration is only stable in magnetic fields above 10 kOe.

Magnetic vortex nucleation/annihilation in artificial-ferrimagnet microdisks

“…[22][23][24][25][26][27] As we observed previously, 26,27 if an artificial ferrimagnet is composed of thin layers of Py and Gd, the heterostructure has very low anisotropy which is comparable with that of Py.…”

“…Magnetic and structural properties of the Py/Gd multilayers have been studied by us 26,27 and other groups 25,29,30 previously.…”

“…At the same time, it was demonstrated that the influence of material intermixing becomes significant for multilayers with thin Py and Gd layers. 26,27 The temperature dependences of magnetization for the [Py(t)/Gd(t)]25 (t=1 or 2 nm) control films are shown in Fig. 1(a).…”

“…We adopted this model for micromagnetic simulations of magnetization behavior for the [Py(1 nm)/Gd(1 nm)]25 disks. The analysis 26,27 showed that the magnetic and atomic structures of the [Py(2 nm)/Gd(2 nm)]25 superlattice is more complicated. According to our estimates, 26,27 only the 0.5-nm thick core parts of the Py and Gd layers are not subjected to intermixing, while the rest of the film is the PyGd alloy.…”

“…The analysis 26,27 showed that the magnetic and atomic structures of the [Py(2 nm)/Gd(2 nm)]25 superlattice is more complicated. According to our estimates, 26,27 only the 0.5-nm thick core parts of the Py and Gd layers are not subjected to intermixing, while the rest of the film is the PyGd alloy. Once it is assumed that the disks are composed of a homogeneous material, the effective exchange stiffness of this material at different temperatures must be estimated.…”