Magnetoresistance of nanocarbon structure modified by NiFe

The paper presents the results of studies of the magneto-transport properties of nanocarbon structures modified on the surface at the same time with particles of transition metals nickel and iron. Two different types of nanocarbon structures were chosen as starting materials for modification. These are graphite nanoplates with lateral particle sizes up to 10 μm, obtained by sonication of thermally exfoliated graphite during several hours in acetone, and multi-walled carbon nanotubes with a diameter of up to 40 nm. The modification of nanocarbon was carried out by the method of metal reduction on the surface of the nanocarbon particles from an aqueous solution of nitrate, which permeated the corresponding nanocarbon particles. As a result of the modification, nanocarbon structures with a uniform distribution of metal particles on the surface of the nanocarbon particles were obtained. The total mass concentration of the metal on the nanocarbon surface was 60%. Studies of the structural and phase composition of the obtained modified nanocarbon structures revealed that on the surface of the modified nanocarbon there are not individual granules of nickel and iron, but FeNi3 alloy particles. To measure the resistance in the magnetic field, bulk samples from modified graphite nanoplatelets and multiwalled carbon nanotubes powders were produced in the form of rectangular parallelepipeds by cold pressing using polyvinyl acetate (25% by mass) as a binder. Measurements of magnetoresistance were carried out by the standard four-probe method at temperatures of 293 K and 77 K and with transverse and longitudinal orientation of the sample relative to the external magnetic field. Conducted experimental studies of magnetoresistance revealed that for modified layered nanocarbon structures, the main contribution to magnetoresistance is made by anisotropic magnetoresistance, which is characteristic of magnetic metals, and linear magnetoresistance, which occurs for layered systems with a zero-band gap and a quasi-linear dispersion law. For modified multi-walled carbon nanotubes, the magnetoresistance properties are determined mainly by the spin-orbital interaction of charge carriers with the magnetic moments of the atoms of the modifier alloy.