Magnetoresistance in amorphous oxide filmsY. Luo1, M. Eßeling1, K. Zhang2, G. Güntherodt3 and K. Samwer1
1 I. Physikalisches Institut, Universität Göttingen - Friedrich-Hund-Platz 1 D-37077 Göttingen, Germany
2 II. Physikalisches Institut, Universität Göttingen - Friedrich-Hund-Platz 1 D-37077 Göttingen, Germany
3 II. Physikalisches Institut, RWTH Aachen - Templergraben 55 D-52056 Aachen, Germany
received 15 July 2005; accepted in final form 1 December 2005
published online 21 December 2005
This paper shows results on structural and magnetotransport measurements for reactively sputtered amorphous oxide films ( with and their layered structures. A strong x-dependency was found to be related to microstructural changes caused by oxygen-induced chemical phase separation. For low x, pair-correlated atom clusters dominate and the films are soft ferromagnetic with excellent uniaxial magnetic anisotropy. Small coercivity Oe, enhanced magnetisation emu/cm3 and low resistivity cm were measured for these films, showing a good potential for application in magnetoelectronics. For large x, however, since - pair-correlated atom clusters are dominant, the films become granular-like superparamagnetic with a saturation field Hs > 20 kOe and a remanence . is extremely high presumably due to Coulomb blockade effect. A large magnetoresistance was observed, being 30% (70 kOe) at 5 K and 10% at room temperature. This effect can be attributed to spin-dependent tunnelling among lateral separated - clusters. The layered structure shows a small, but low-field magnetotunnelling effect.
75.70.-i - Magnetic properties of thin films, surfaces, and interfaces.
75.50.-y - Studies of specific magnetic materials.
© EDP Sciences 2006