Magnetoresistive Properties of Multilayer Film Systems Based on Permalloy and Silver

In this paper, the experimental investigation focuses on the magnetoresistive properties of nanosized film systems. Their structure changes from layered to granular due to transition from bilayer FM/NM (FM is a ferromagnetic material, NM is a nonmagnetic material) to [FM/NM]n multilayer film at a constant total thickness of samples. As ferromagnetic and nonmagnetic materials were chosen permalloy Ni80Fe20 (Py) and Ag, respectively. It was demonstrated that the shape of the field dependences of magnetoresistance depends on the number of bilayer Py/Ag. For as-deposited [Py/Ag]n/S at n = 8, 16, the transition from the antiferromagnetic ordering of magnetic moments to ferromagnetic one occurs under an external magnetic field. As a result, the resistivity of the samples reduced, and the giant magnetoresistive effect was realized. The increase of the number of bilayers repeats from 2 to 16 at the unchanged total thickness of the system leads to the growth of the magnetoresistance from 0.1 % to 0.35 %. During annealing up to 600 K, the magnetoresistive effect is reduced, but it does not disappear completely

Гигантский магниторезистивный эффект в отражении микроволн от сверхрешеток (CoFe)/Cu

Experimental study of microwave giant magnetoresistive effect in wave reflection has been carried out in frequency range from 26 to 38 GHz. The magnitude of the effect is obtained and its magnetic field dependence is defined. The experiments are carried out with (CoFe)/Cu superlattices, which have giant magnetoresistance. Calculations of the magnetic field dependence of microwave reflection coefficient are fulfilled. The measured values of reflection coefficient variations are found to be greater than the calculated ones. This difference is connected with approximation within which the superlattice is replaced by the uniform metallic plate in calculations. A frequency dependence of microwave giant magnetoresistive effect in reflection is also observed. This dependence is explained by the influence of the waveguide impedance where the sample is placed in measurements.

Ферромагнитных резонанс в прохождении электромагнитных волн через металлические сверхрешетки

Variations of microwave transmission coefficient through Fe films and Fe/Cr superlattices have been studied caused by ferromagnetic resonance at frequencies from 26 to 38 GHz. The shape of resonance line is described in frames of the model where its asymmetry is obtained by adding of lorenzian dispersion line to the absorption line. It has been shown that the shape of resonance line for superlattices with continuous Fe and Cr layers and also for Fe films is well described in this model. For the superlattices with thin Fe or Cr layers only qualitative agreement is observed. In magnetic fields less than the field of ferromagnetic resonance, essential distinction is observed of experimental magnetic field dependence of transmission coefficient comparing to the model, for superlattices which have giant magnetoresistive effect.

Microsystems with High Conversion Coefficient of a Weak Magnetic Field Based on Magnetoresistive Nanostructures

The magnetoresistive transducers of magnetic field have been claimed both for direct and indirect applications in various areas of industry, transport and special equipment. In the paper the special features of used terminology and dimensions in the main parameters of magnetic field magnetoresistive transformers have been revealed. The main results of experimental studies on the developed thin-film magnetoresistive nanostructures (TMN) with even and odd transfer characteristics have been presented. The TMN design on an anisotropic magnetoresistive effect has an odd transfer characteristic and conversion coefficient at the level of 8 mV/V/E. The TMN design based on a giant magnetoresistive effect has an even transfer characteristic and a conversion coefficient at the level of 27 mV/V/E. The results of promising design and technological solutions allowing reaching the values of conversion coefficient of TMN at the level exceeding 100 mV/V/E have been shown. The results of the study of the test spin-tunnel magnetoresistive nanostructure (spin-tunnel TMN) with giant magnetoresistive effect, exceeding 100% have been presented. The novelty of the obtained results has been reflected and the perspective of using highly sensitive TMN and creating the non-volatile MRAM on the basis of thin-film magnetoresistive structure with the spin-tunnel magnetoresistive effect have been determined.

Caused by the giant magnetoresistive effect changes of microwave refractive index

Studies of the interaction of electromagnetic microwaves with [Co88Fe12/Cu]n, nanostructures, in which the giant magnetoresistive effect (GMR) shows itself, have been carried out. It is established that the GMR effect contributes to changes in the microwave complex refraction coefficient, including the refractive index.