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The influence of microstructure on tunnelling magnetoresistance in Fe-SiO 2 granular films

2000; Institute of Physics; Volume: 33; Issue: 6 Linguagem: Inglês

10.1088/0022-3727/33/6/306

1361-6463

Li Xi, Zongzhi Zhang, Jianbo Wang, Chengxian Li, Fashen Li, Shihui Ge, Tao Xu, Shengrong Yang,

Magnetic Properties and Applications

The influence of film thickness on the microstructure and tunnelling magnetoresistance (TMR) in Fe-SiO2granular films has been systematically studied using x-ray diffraction, transmission electron microscopy (TEM) and Mössbauer spectroscopy. The results indicate that the average Fe granule size and the size distribution, as well as the interface between the granules and SiO2matrix, sensitively depend on the film thickness, which modifies the TMR effect. For the very thin films, the TEM image shows an indistinct interface between the Fe particles and SiO2matrix, and the corresponding Mössbauer spectrum shows the existence of a strong non-magnetic Fe2 SiO4component, which is responsible for the small TMR of this film. While for the thickest film, the long sputtering time makes the Fe granules grow so large as to aggregate some of them, which also leads to the small TMR. The optimum thickness in our samples is 0.55 µm, which gives the largest TMR value of -3.3% at room temperature under a field of 1.6 T due to the uniform size of the small particles and the few in the Fe2 SiO4phase. Our results give evidence that small Fe particles with a narrow size distribution and without oxidation favours the TMR effect.