Tunnel Magnetoresistive Effect in Nanostructured Composite Systems

O.V Stognei,Yu.E Kalinin,A.V Sitnikov,N Perov,A Semisalova

doi:10.1051/epjconf/201818501016

Abstract

The results of the investigation of tunnel magnetoresistive effect in a large number of metal-dielectric nanocomposites obtained by the same technology and under identical conditions are presented. The composites with multi-elemental amorphous metal phase were considered. It has been shown that the large values of the tunnel magnetoresistive effect in these composites are ensured when the value of the density of electronic states on the Fermi surface is large while other conditions are being equal. The conditions for the appearance of an anomalous positive tunneling magnetoresistance are formulated based on the study of composites with a mono-elemental ferromagnetic phase from cobalt.

Highlights

Nanogranular composites are artificial materials consisting of two different phases
Some experimental results concerning the influence of the metal phase electronic properties as well as composite’s morphology on the tunneling magnetoresistance (TMR) values are presented in the paper
The TMR effect is determined by reorientation of granules magnetic moments under applied magnetic field [13]

Summary

Introduction

Nanogranular composites are artificial materials consisting of two different phases (as a rule – from metal and dielectric materials). The TMR is due to tunneling of spin-polarized electrons between ferromagnetic nanogranules through dielectric barriers [1] Owing to this complicated mechanism the TMR is very sensitive to a large number of different factors [2,3,4]: granule’s size distribution, the distance between granules, presence or absence of clusters coexisting together with separated granules, the magnetic anisotropy of granules, parameters of the tunnel barrier, co-tunneling and interface effects etc. All these features can be observed within one composite system when the ratio between metal and dielectric phases is being changed. Some experimental results concerning the influence of the metal phase electronic properties as well as composite’s morphology on the TMR values are presented in the paper

Methods

Composites with amorphous metal granules

Cobalt based composites and positive TMR

Conclusion