Low field magnetoresistance of intergranular tunneling in field-aligned chromium dioxide powders

摘要

The magnetic and magnetotransport properties of field-aligned single domain half-metallic CrO₂ powders have been studied. Needle-shaped nanoparticles of CrO₂ have been aligned in a strong magnetic field. The aligned powder sample shows a strong anisotropy along the alignment direction. The conduction mechanism of the aligned CrO₂ powder sample has been examined and is consistent with the intergranular spin dependent tunneling. Negative tunneling magnetoresistance (TMR) of about 41% is achieved in a small field in the vicinity of the coercive field at 5 K. The magnetoresistance (MR) versus field curve shows two well-separated narrow peaks at the coercive fields and resembles that of a magnetic tunnel junction. This junction-like MR results from the narrow switching field distribution of the aligned powders. The results suggest that the aligned magnetic CrO₂ particles may find novel applications in spin transport structures and devices.