Critical behavior of resistivity and Hall resistivity in percolating ferromagnetic metal-insulator films

✍ Scribed by A.B. Pakhomov; X. Yan

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 461 KB
• Volume: 229
• Category: Article
• ISSN: 0378-4371
• DOI: 10.1016/0378-4371(96)00023-4

✦ Synopsis

Resistivity pxx and Hall resistivity pxy were measured as functions of the magnetic field, temperature, and the metal volume fraction x, on a series of percolating Ni-Si02 granular films. At 5 K, the data for the metallic samples were fitted to power law dependencies of the forms, pxx ~ [(x -xc)/xc] -t and pxy OC [(X --Xc)/Xc] -g, with xc = 0.6. The critical exponents of the resistivity t = 2.7 4-0.2, the extraordinary Hall resistivity gs = 2.0 4-0.2 and the ordinary Hall resistivity go = 1.8 4-0.3 were found to be notably larger than the predictions for discrete percolation models (t ~ 2 and g ,-~ 0.4-0.5). We suggest that a percolation model incorporating localization can explain that contradiction. In the region of transition from metallic conduction to thermally activated tunneling, 0.53 < x < 0.6, the extraordinary Hall resistivity pxy.~ was found to be saturated at a value > 100p, f~cm, which is almost four orders of magnitude greater than that of pure Ni.