Tunnel magnetoresistance in Co nanoparticle/Co–C60 compound hybrid system

Abstract

Co-ITO granular magnetoresistance films fabricated by precipitation of magnetic nanoparticles from amorphous oxide J.A nanometer-scale hybrid film of Co particle/Co-C 60 compound was prepared by alternate deposition of Co and C 60 under UHV condition. All of Raman spectra, magnetization curves, and tunnel conductivity concluded that the hybrid system has a granular structure consisting of Co nanoparticles embedded in a Co-C 60 compound matrix. The magnetoresistance ratio of 26% was obtained at 2 K and 10 kOe for the electron tunneling across the Co-C 60 compound barrier. In addition, anomalously large bias voltage dependence was found in the magnetotransport properties.

Magnetic and Magnetotransport Properties in Nanogranular Co/C<SUB>60</SUB>-Co Film with High Magnetoresistance

“…The dominated conductivity by the smaller Co nanoparticles might be associated with the nonsaturating MR-H curves at high field. Figure 7 shows examples of the V dependences of the MR(10 kOe) measured at 2 K, 4.2 K and 8 K, 16) respectively. The MR(10 kOe) at 4.2 K shows a decreasing tendency from 24% to the minimum value of 17% with increasing V in the LB region.…”

“…[10][11][12][13][14][15] Very recently, we have shown that the alternately (alt-) deposited C 60 -Co film exhibits the remarkable TMR ranging from 10% to 80%. 16,17) In the present paper, magnetic properties of the altdeposited Co/C 60 -Co film are described, and the structure and the magnetic field/bias voltage dependent magnetotransport behaviors 16,17) are discussed based on them.…”

Voltage-controlled spin injection with an endohedral fullerene Co@C60 dimer

“…3 for P versus V G indicate that the spin injection can be controlled by changing the gate voltage and positive or negative values for the spin polarization may be obtained, depending on the value and the sign of gate potential. The magnitude of P can exceed 90% for certain values of gate voltage which is considerably higher than that calculated for Co-nanowire@CNT (66%) [5] and those measured for Co-cluster/C 60 mixtures (70%) [7], Co-nanoparticle/Co-C 60 compounds (40%) [11] and Co crystals (42%) [48].…”

“…For example, ab initio calculations showed that Co atoms in CNTs can provide strong spin polarization and considerable magnetic moments [5]. The electrical and magnetic properties of C 60 -Co nanocomposites have also been studied [7,11,12] and tunnel magnetoresistance ratios up to about 30% at low bias voltages were reported, indicating significant spin polarizations [7]. Recent density functional theory (DFT) studies of encapsulated Co atoms in C 60 molecules [18] found hybridization between Co and C 60 orbitals and the most stable structure of Co@C 60 to have the Co atom on top of a hexagonal face.…”

“…One way to generate a spin-polarized charge current is to encapsulate magnetic atoms or magnetic nanowires in fullerenes or CNTs [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. For example, ab initio calculations showed that Co atoms in CNTs can provide strong spin polarization and considerable magnetic moments [5].…”