In this paper, we report a study of evolution of low field magnetoresistance (MR) of Gadolinium as the grain size in the sample is changed from few microns (∼4 μm) to the nanoscopic regime (∼35 nm). The low field MR has a clear effect on varying grain size. In large grain sample (few μm), the magnetic domains are controlled by local anisotropy field determined mainly by the magnetocrystalline anisotropy. The low field MR clearly reflects the temperature dependence of the magnetocrystalline anisotropy. For decreasing gain size, the contribution of spin disorder at the grain boundary increases and enhances the local anisotropy field.
Magnetization reversal and magnetoresistance behavior of perpendicularly magnetized [Co/Pd]4/Au/[Co/Pd]2 nanowiresWe report low field (l 0 H < 0.2 T) magnetoresistance (MR) studies on a single Gd nanowire patterned from a nano-structured film (average grain size $ 35 nm) by focused ion beam. For comparison, we did similar MR measurements on a polycrystalline sample with large crystallographic grains ($4 lm). It is observed that in the low field region where the MR is due to motion of magnetic domains, the MR in the large grained sample shows a close relation to the characteristic temperature dependent magnetocrystalline anisotropy including a sharp rise in MR at the spin reorientation transition at 235 K. In stark contrast, in the nanowire, the MR shows complete suppression of the above behaviours and it shows predominance of the grain boundary and spin disorder controlling the domain response. V C 2014 AIP Publishing LLC. [http://dx.
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