Comparative study of magnetoresistance and magnetization in nano-oxide specular and nonspecular MnIr/CoFe/Cu/CoFe spin valves from 10 to 300 K

• Published in: Journal of applied physics 2002-04, Vol.91 (8), p.5321-5324
• Main Authors: Sousa, J. B., Ventura, J. O., Salgueiro da Silva, M. A., Freitas, P. P., Veloso, A.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.1459617

The temperature and magnetic field dependences of the magnetoresistance (MR), superconducting quantum interference device magnetization M, its electrical resistance R and temperature derivative dR/dT (10–300 K) are reported for nonspecular CoFe/Cu/CoFe spin valves and specular spin valves formed by nano-oxidation of the pinned and free CoFe layers. The MR(T) increases linearly with decreasing temperature on both spin valves, and data extrapolation converges to zero MR practically at the same Curie temperature. At temperatures below ∼175 K the specular spin valve MR(H) curves present two anomalous bumps not seen in the nonspecular curves. Also, for the nonspecular spin valve a clear relation is visible between M and MR curves, which is not the case for the specular spin-valve curves. In the specular spin valve, dR/dT presents an anomalous enhancement after T∼150 K, which is discussed in terms of electron scattering in the nano-oxide layers. The application of a saturating magnetic field suppresses most of the anomaly, indicating its magnetic origin.