Size dependence of Peltier cooling in ferromagnet/Au nanopillars

We study Peltier cooling in current-perpendicular-to-plane multilayer nanopillars with diameters D varying from 60 to 430 nm and made from Au and various ferromagnets (FMs): Heusler compounds Co2MnSi and Co2FeSi (CFS) and conventional FM metals Fe and Co. We report an enhanced effective Peltier coefficient ΠCPP in resistance–current curves at small D (<120 nm). The maximum ΠCPP value of about 165 mV, found for the CFS/Au interface with D ~ 60 nm, is 24 times higher than the bulk Peltier coefficient Πbulk (~7 mV) and corresponds to a high cooling power of 43.6 MW/cm2.