Tunable magneto-Seebeck effect in CoFeSi/MgO/CoFeSi heterostructure via optimized interfacial engineering

Enhancing the tunneling magneto-Seebeck（TMS） ratio and uncovering its underlying mechanism are greatly demanded in spin caloritronics.The magnitude and sign of the TMS effect depend on the type of atom and the stacking order of atoms at the interfaces.Herein,we demonstrate that TMS ratios can be effectively manipulated by altering heterogonous or homogeneous interface through decoration on the CoFeSi（001） surface inserted on the MgO insulating layers.The maximum TMS ratio of pure Co2/O termination is 4565% at 800 K.Notably,the TMS ratio of the FeSi/O termination has two peak values,of which the maximum could reach up to-3290% at 650 K.By comparing two different atom arrangements at the interface,we reveal that the sign and symbol of the TMS ratio can be controlled by the temperature and different atomic configurations at the Co2FeSi/MgO interface.Furthermore,the spin-Seebeck coefficient up to ～150 μV/K is also possible when we select suitable terminations and temperatures.These findings will provide useful insights into how to control the sign and symbol of the TMS ratio and accordingly stimulate the development field of magneto-thermoelectric power and spin caloritronic devices based on the magneto-Seebeck effect in Heusler-based metallic multilayers.