‘Giant’ magnetoresistance in obliquely co-evaporated Co-Ag films

Abstract

Magnetoresistance (MR) measurements at room temperature have been performed on obliquely (co-1 evaporated Ag-Co films deposited at room-and elevated-temperatures.The 'giant' magnetoresistance ratio (max. 13% for a composition of about Co&g,) over a wide range of compositions has been measured. The films are polycrystalline and grown in a columnar morphology. The columnar diameter depends on the thickness and is < 20 nm at 400 nm thickness. From XRD, NMR and saturation magnetization (it&l vs. at% Ag, one can conclude that the films consist of Co-Co and Ag-Ag clustersThe coercivity depends on the thickness of the films @IO-700 nm) and varies from 5 to 15 kA/m.

Effect of chemical composition and Co-core size on the magnetic and magneto-transport properties of CoyAg100−y core–shell nanocrystallites

“…However, when the measurements were carried out at 5 K, two out of a total of seven samples studied in this investigation exhibit a considerable MR effect. For illustration, Figure 9 5 , which all consist of a core-shell structure of small fcc-Co crystallites with primarily an fcc-Ag in part the shell on the individual crystallites. It could be observed that the first two samples (a) and (b) in Figure 9(A) exhibit a significant change in their electrical resistance within an applied field swept from (¡)10 to (C)10 kOe, whereas the sample (c) which consists of an average Agcontent of 51.5 at% does not show any significant change in its electrical resistance under similar conditions of the field and temperature.…”

“…4 , while vanished completely in the third sample Co 48.5 Ag 51. 5 . From these results, it could be observed that a strong dependence exists between the chemical composition and Co-core size in a core-shell structure and the MR properties.…”

“…Synthesis and characterisation of magnetic core-shell nanocrystallites (CSNCs) has gained prominence due to their potential applications in diverging fields such as magnetic recording, magnetic sensing, catalysis, diagnosis, drug delivery and bio-separations [1][2][3][4][5]. The physical, chemical and magnetic properties of CSNCs can be tuned by controlling the core and shell thicknesses as well as their chemical composition [6].…”

“…The giant magneto resistance (GMR) effect is a unique phenomenon exhibited by Co y Ag 100¡y CSNCs, and it leads to potential applications in many areas such as magnetic field sensors and recording media [4,5]. Various physical methods such as sputtering and mechanical alloying have thus far been reported for the preparation of Co y Ag 100¡y nanometric thin films or nanocomposites [5,10].…”

“…Various physical methods such as sputtering and mechanical alloying have thus far been reported for the preparation of Co y Ag 100¡y nanometric thin films or nanocomposites [5,10]. However, true core-shell structures are envisaged as better alternative over thin films or composites as the particle size could be effectively controlled to near ideal situation of two ferromagnetic single domains separated by a non-ferromagnetic layer.…”