Enhanced spin Seebeck effect via oxygen manipulation
Jeong-Mok Kim, Seok-Jong Kim, Min‐Gu Kang, Jong-Guk Choi, Soogil Lee, Jaehyeon Park, Phuoc Cao Van, Kyoung‐Whan Kim, Kab‐Jin Kim, Jong‐Ryul Jeong, Kyung‐Jin Lee, Byong‐Guk Park
Abstract
Abstract Spin Seebeck effect (SSE) refers to the generation of an electric voltage transverse to a temperature gradient via a magnon current. SSE offers the potential for efficient thermoelectric devices because the transverse geometry of SSE enables to utilize waste heat from a large-area source by greatly simplifying the device structure. However, SSE suffers from a low thermoelectric conversion efficiency that must be improved for widespread application. Here we show that the SSE substantially enhances by oxidizing a ferromagnet in normal metal/ferromagnet/oxide structures. In W/CoFeB/AlO x structures, voltage-induced interfacial oxidation of CoFeB modifies the SSE, resulting in the enhancement of thermoelectric signal by an order of magnitude. We describe a mechanism for the enhancement that results from a reduced exchange interaction of the oxidized region of ferromagnet, which in turn increases a temperature difference between magnons in the ferromagnet and electrons in the normal metal and/or a gradient of magnon chemical potential in the ferromagnet. Our result will invigorate research for thermoelectric conversion by suggesting a promising way of improving the SSE efficiency.