A research team led by Prof. Dr. Hartmut Zabel of Ruhr-Universitaet-Bochum (RUB) has for the first time experimentally confirmed the spin pumping effect, an important physical phenomenon, in magnetic layers.
RUB physicists study about the dynamics in spin valves
The RUB research team had conducted the study in the ALICE test chamber constructed by the university physicists in Berlin. The team has successfully measured the spin pumping effect utilizing ultrafast X-ray scattering technique with a resolution of picoseconds. Single electrons due to their magnetic precession can reciprocally control each other’s spin via a non-magnetic intermediate layer. This is an important finding to develop the next-generation magnetic sensors for hard disk read heads and other data storage devices.
During the study, the research team used a copper layer to separate two ultra-thin magnetic layers. The thickness of the copper layer was large enough to prevent influence or at least static influence between the two ferromagnetic layers. However, the magnetic precession’s damping is based on the second magnetic layer’s orientation subsequent to the stimulation of one of the two ferromagnetic layers to an ultrafast precession in the gigahertz range. The damping is higher if both layers have orientation in opposite directions and it is lower damping if both are oriented in the same direction.
The magnetic precession in a ferromagnetic layer is pumped via the non-magnetic intermediate copper layer and then imbibed by the second ferromagnetic layer. i.e., ferromagnetic layers, which do not communicate with each other in the static state due to the thickness of the intermediate layer, can still influence each other dynamically via diffusion and pumping of spins between the layers.
For the study, the research team used a sequence of layers of a typical spin valve, which are nano-magnetic layer structures utilized as magnetic sensors in hard disks’ read heads and they encode the logical bits (“0” and “1”) in non-volatile magnetic data storage. The pace, at which data can be written and read is based on the magnetic precession and its damping. The discovery that magnetic precession’s damping is affected by spin pumping via non-magnetic intermediate layers is not only of basic interest but also finds use in industrial applications, Zabel said.