Comparative study between charge and spin thermoelectric figure of merits in an antiferromagnetic ring

Abstract

Abstract Considering the unique and diverse characteristic features of antiferromagnetic (AFM) systems, here in our work, we explore spin-dependent thermoelectric behavior in an AFM ring geometry. A reasonably large ( ≫ 1 ) spin figure of merit, referred to as Z S T, is obtained under suitable input conditions. Two important prerequisites are (i) breaking the symmetry among up and down spin sub-Hamiltonians and (ii) generating different asymmetric transmission line shapes across a Fermi energy for two opposite spin electrons. Describing the physical system within a tight-binding framework, where spin-dependent scattering occurs due to the interaction of itinerant electrons with local magnetic moments via the usual spin-moment exchange interaction, we compute all the thermoelectric quantities based on Landauer integrals following the Green’s function technique. The behavior of charge figure of merit, denoted as Z C T, is also discussed along with Z S T. Though Z C T reaches above unity, it is much smaller compared to Z S T. This is the key finding of our investigation. To make the present communication a self-contained one, we compare the results with another arrangement of magnetic moments in a ring-like geometry and in a chain-like one. Our analysis gives a suitable hint that in the presence of spin-dependent scattering, much more favorable energy conversion can be substantiated.