Spin torque MRAM using bidirectional magnonic writing

An apparatus is provided for bidirectional writing. A stack includes a reference layer on a tunnel barrier, the tunnel barrier on a free layer, and the free layer on a metal spacer. The apparatus includes an insulating magnet. A Peltier material is thermally coupled to the insulating magnet and the stack. When the Peltier/insulating magnet interface is cooled, the insulating magnet is configured to transfer a spin torque to rotate a magnetization of the free layer in a first direction. When the Peltier/insulating magnet interface is heated, the insulating magnet is configured to transfer the spin torque to rotate the magnetization of the free layer in a second direction.