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Negative Magnetoresistance at High Magnetic Fields in Granular Aluminum


  Nimrod Bachar [1,2]  ,  Shachar Lerer [1]  ,  Shay Hacohen-Gourgy [1]  ,  Boaz Almog [1]  ,  Guy Deutscher [1]  
 [1] School of Physics and Astronomy, Tel Aviv University, Tel Aviv, 69978, Israel
[2] Laboratory for Superconductivity and Optical Spectroscopy, Ariel University Center, Ariel, 40700, Israel

Since the discovery of granular Aluminum by Abeles et al.[i], the mechanism for the enhancement in its Tc, up to a factor of three from bulk Aluminum, is still unrevealed. Following earlier works[ii],[iii], we measured the magnetoresistance (MR) of granular Aluminum thin films with typical grain size of 2 nm. We show that the MR is negative, with no observed saturation, up to high magnetic fields of 30T and high temperatures of ~100K. We also show that the MR effects in our films are doping dependent. We will discuss several interpretations for this negative behavior in the normal state and its possible correlation with the enhancement of Tc in granular Aluminum. 

[i] B. Abeles, R. Cohen, and G. Cullen, Physical Review Letters 17, 632-634 (1966).

[ii] K. Mui, P. Lindenfeld, and W. McLean, Physical Review B 30, 2951-2954 (1984)

[iii] A. Gerber, A. Milner, G. Deutscher, M. Karpovsky, and A. Gladkikh, Physical Review Letters 78, 4277-4280 (1997).