Tracking the evolution of magnetic ordering in Co/Ru multilayers with inhomogeneous interlayer coupling using polarised neutron reflectometry

We report the measurement of reflected neutron intensity “hysteresis loops” from Co/Ru multilayers that have both antiferromagnetically and ferromagnetically coupled regions. We show that by measuring the four neutron spin-resolved reflectivities at a particular value of wavevector transfer, the normalised value of the relevant magnetic order parameter may be determined. The response of that order parameter to an applied magnetic field may hence be tracked. We have benchmarked our results against conventional magnetometry and magnetotransport measurements.