Magneto-resistance of Nano-Fe₃O₄/Ag Granular System

抄録

Four kinds of Fe₃O₄/Ag granular systems were prepared from sintered mixtures of Fe₃O₄ and Ag or Ag₂O. Magneto-resistances (MR_s) were measured at room temperature for samples with Ag volume fraction x between 0 and 0.4. Samples including relatively large Fe₃O₄ grains showed -1% to -1.4% room temperature MR ratios (MRR) at 1 T. On the other hand, samples including Fe3O4 nano-particles showed large negative room temperature MRR of about -4% to -5% at 1 T near the percolation threshold of χ_c-0.2. It was suggested that Fe₃O₄/Ag/Fe₃O₄ paths were effective for the large IMRRI by the elastic conduction of spin-polarized electrons between Fe₃O₄ nano-particles. Possibility of spin accumulation in small Ag particles was also shown for this system.