Origin of the exchange bias training effects in magnetically coupled soft/hard synthetic bilayers at low temperature

Hysteresis loops of the nanoscale magnetic layer Co₉₀Fe₁₀ and Ni₈₁Fe₁₉ and bilayer Co₉₀Fe₁₀/Ni₈₁Fe₁₉ and Ni₈₁Fe₁₉/Co₉₀Fe₁₀ films were measured as a function of external dc magnetic field and the thickness dependence of these films were plotted as a function of temperature. Time evolution of the minor/middle/major hysteresis loops of 5/5 nm-thick Ni₈₁Fe₁₉/Co₉₀Fe₁₀ monolayer have been observed at 10 K. The spin valve, exchange bias training and Barkhausen effects for magnetic layer and bilayer films have been analysed at various temperatures, thicknesses and different orientations according to the substrate. The exchange-bias training effects have been observed only in positive magnetization region. Origin of the exchange-bias training effects and asymmetric hysteresis loops are related to the relaxation mechanism of a pinning layer in magnetically coupled soft/hard bilayers