Spin-to-Charge Conversion Without Magnetic Electrodes
A central goal of spintronics is to create and manipulate spin-polarized currents. Typically, spintronic devices rely on magnetic electrodes for spin injection. However, a graphene–antiferromagnet interface could potentially offer a more efficient and energy-saving way to control current, functioning like an electrostatic gate. Theorists have predicted that magnons—collective spin excitations in a material—could couple to electrons at this interface, thereby mediating electron transport. Now Sujan Maity of the Indian Association for the Cultivation of Science and his colleagues have measured the predicted electron–magnon coupling [1]. The interaction at the interface allows for direct spin-to-charge conversion without the need for magnetic electrodes.
The researchers created two different types of 2D heterostructures, each consisting of an antiferromagnetic layer (FePS3) sandwiched between few-layer graphene in a different orientation. Applying an electric field parallel to the graphene surface produced an electric current and, with it, a magnetic field perpendicular to the surface. Measuring electrical and magnetic properties in each device revealed two main features. First, magnon “stiffness”—a measure of resistance to spin deformation in the antiferromagnetic layer—decreased as the temperature was lowered. Second, the graphene layer exhibited negative magnetoresistance—a decrease in resistivity in response to an external magnetic field—at temperatures as high as 100 K. Negative magnetoresitance typically occurs at significantly lower temperatures.
To investigate these unexpected findings, the researchers turned to analytical models based on charge–magnon interactions. The coupling was described through an interaction that exchanges angular momentum between electron spins and magnons. Notably, the presence of a magnetic field plays a crucial role in this process, leading to magnon-to-charge conversion at the interface. The measurements and their explanation could hasten the development of spin-based logic devices and magnetic sensors.
–Rachel Berkowitz
Rachel Berkowitz is a Corresponding Editor for Physics Magazine based in Vancouver, Canada.
References
- S. Maity et al., “Electron-magnon coupling mediated magnetotransport in antiferromagnetic van der Waals heterostructures,” Phys. Rev. B 111, L140407 (2025).