Breaking voltage-controlled magnetic anisotropy-magnetoresistance trade-off for ultralow-energy switching in magnetic tunnel junctions.

Electric-field control of spin states offers a promising route to ultralow-power, ultrafast magnetization switching in spintronic devices such as magnetic tunnel junctions (MTJs). However, enhancing voltage-controlled magnetic anisotropy (VCMA) through interfacial engineering often disrupts coherent tunneling and suppresses tunnel magnetoresistance (TMR), limiting practical device performance. Here, we experimentally demonstrate highly energy-efficient, voltage-driven magnetization switching in MTJs enabled by a remote iridium (Ir) doping strategy that tailors the Ir concentration near the MgO/CoFeB interface in the free layer. By inserting an ultrathin Ir layer away from the tunnel barrier and leveraging controlled diffusion during annealing, we achieve sub-nanosecond switching with an energy of only 3.5 femtojoules per bit in nanoscale MTJs while maintaining a TMR ratio up to 160% after 400°C postannealing. These results resolve a long-standing VCMA-TMR trade-off and establish a scalable pathway toward ultralow-power nonvolatile spintronic devices under aggressive energy and scaling constraints.