Noncollinear Magnetization Between Surface and Bulk Y3Fe5O12
Po-Hsun, Wu1*, Ssu-Yen Huang1
1Physics, National Taiwan University, Taipei, Taiwan
* presenting author:Po-Hsun Wu,
Yttrium iron garnet (YIG, Y3Fe5O12) is a magnetic insulator that has been widely used to generate spin-wave spin current via the longitudinal spin Seebeck effect (LSSE). Spin current can be converted to charge current by the inverse spin Hall effect (ISHE) with a spin direction given by the magnetization of the YIG. However, in the low-field range, both the ISHE voltage from the thermal transport measurement and the magnetoresistance (MR) from the electrical transport measurement are inconsistent with the magnetization reversal behavior of the YIG slab with an unusual plateau feature in the metal/YIG bilayer structure.
In this work, we provide direct evidences to demonstrate that the plateau behavior in the thermal and electrical transport measurement of metal/YIG is due to the noncollinear magnetization configuration between the bulk and surface of YIG. In addition, by keeping the measured surface of YIG unaltered, we show that the YIG surface magnetization can be systematically controlled by varying the thickness. Therefore, the noncollinear magnetization is the intrinsic property of the bulk YIG and is independent of the growth method, chosen substrate, and crystal orientation. Our results show that the thermal spin current can function as a sensitive tool to study the surface magnetization configuration of materials.

Ref.: P. H. Wu and S. Y. Huang, Phys Rev. B 94, 024405 (2016)

Keywords: Spin Seebeck effect, Spin transport, Noncollinear magnetization