A platform for time-resolved scanning Kerr microscopy in the near-field.

Time-resolved scanning Kerr microscopy (TRSKM) is a powerful technique for the investigation of picosecond magnetization dynamics at sub-micron length scales by means of the magneto-optical Kerr effect (MOKE). The spatial resolution of conventional (focused) Kerr microscopy using a microscope objective lens is determined by the optical diffraction limit so that the nanoscale character of the magnetization dynamics is lost. Here we present a platform to overcome this limitation by means of a near-field TRSKM that incorporates an atomic force microscope (AFM) with optical access to a metallic AFM probe with a nanoscale aperture at its tip.

Coresonant enhancement of spin-torque critical currents in spin valves with a synthetic-ferrimagnet free layer.

It is experimentally shown that the critical current for onset of spin torque instability in current-perpendicular-to-plane spin valves can be strongly increased using "synthetic-ferrimagnet" free layers of form FM1/Ru/FM2 (FM=ferrromagnet). However, this increase occurs for only one polarity of bias current. A two-macrospin model is shown to reproduce the observations.