THE HALL EFFECT AND MICROSTRUCTURES OF (Fe_0.86Zr_0.033Nb_0.033B_0.068Cu_0.01)_x(Al₂O₃)_1-xGRANULAR FILMS

Abstract

A series of ( Fe 0.86 Zr 0.033 Nb 0.033 B 0.068 Cu 0.01 ) x ( Al 2 O 3 ) 1-x granular films of about 100 nm thick were deposited on the glass substrate using the magnetron sputtering technique. Hall resistivity was measured using a four-terminal method at room temperature in the field of 1.1 Tesla. As x increases, the Hall resistivity of the samples rises and reaches a maximum of 17.5 μΩ-cm at x = 0.43, which is about three orders of magnitude greater than those of pure magnetic metal samples, and for further increase of x, the Hall resistivity decreases. For as-deposited x = 0.43 sample, transmission electron microscopy (TEM) images shows the microstructural characteristics of granular films around percolation threshold. The temperature dependence of resistivity shows that the conduction behavior changes from insulator to metal with the increment of metal fraction, and for sample x = 0.43, the conduction behavior is located in the transition region from insulator to metal, near the percolation value, which is consistent with the above experimental results. It is suggested that the enhancement of Hall effect results from not only the magnetic metal fraction but also the microstructure characteristic of percolation system.