  To mitigate climate change, our global society is harnessing direct (solar
irradiation) and indirect (wind/water flow) sources of renewable electrical
power generation. Emerging direct sources include current-producing thermal
gradients in thermoelectric materials, while quantum physics-driven processes
to convert quantum information into energy have been demonstrated at very low
temperatures. The magnetic state of matter, assembled by ordering the
electron's quantum spin property, represents a sizeable source of built-in
energy. We propose to create a direct source of electrical power at room
temperature (RT) by utilizing magnetic energy to harvest thermal fluctuations
on paramagnetic (PM) centers. Our spin engine rectifies current fluctuations
across the PM centers' spin states according to the electron spin by utilizing
so-called 'spinterfaces' with high spin polarization. As a rare experimental
event, we demonstrate how this path can generate 0.1nW at room temperature
across a 20 micron-wide spintronic device called the magnetic tunnel junction,
assembled using commonplace Co, C and MgO materials. The presence of this path
in our experiment, which also generates very high spintronic performance, is
confirmed by analytical and ab-initio calculations. Device downscaling, and the
ability for other materials systems than the spinterface to select a transport
spin channel at RT widens opportunities for routine device reproduction. The
challenging control over PM centers within the tunnel barrier's nanotransport
path may be addressed using oxide- and organic-based nanojunctions. At present
densities in MRAM products, this spin engine could lead to 'always-on' areal
power densities well beyond that generated by solar irradiation on earth.
Further developing this concept can fundamentally alter our energy-driven
society's global economic, social and geopolitical constructs.
