Magnetotransport properties of nanogranular composites with low-field positive magnetoresistance

• A low-temperature feature is detected in nanogranular magnetic films with perpendicular anisotropy that have a low-field positive magnetoresistance: positive magnetoresistance is observed during the initial magnetization of the demagnetized sample, but is absent when the magnetic field is removed and/or during subsequent magnetizations. This effect is studied using a Co-x(Al2On)(1-x)film withx = 0.60, consisting of Co metal nanogranules in an Al(2)O(n)insulating matrix withnclose to 3. It is found that together with perpendicular anisotropy, the film has local in-plane anisotropy with randomly oriented easy axes, which prevents the reorientation of the granules' magnetic moment projections in the film plane below a certain blocking temperature. The restoration of the local short-range order in the orientation of the magnetic moments of the demagnetized film's neighboring granules, which is optimal for conductivity and is destroyed by the introduction of a magnetic field, is prevented at temperatures below the blocking temperature and is not restored during subsequent cycles of introducing/removing the magnetic field without heating to temperatures above the blocking temperature.

Ämnesord

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

Nyckelord

magnetization reversal processes

nanogranular magnetic films

positive magnetoresistance

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)