A happy marriage between critical phenomena and spintronics (Vol. 49, No. 3)

Schematic drawing of the spin Seebeck effect near the magnetic phase transition

Spintronics is a technology that aims to use spin in information processing for practical application, whereas critical phenomena belong to an academic subject that deals with phase transition. These two seemingly different subfields meet at the interface between a magnetic insulator and a paramagnetic metal. The thermal spin injection from an insulating magnet into the adjacent heavy metal is referred to as spin Seebeck effect. Since its discovery in 2008, this phenomenon has attracted much attention as a simple and versatile means for generating spin current that is needed to drive the functionality of spintronic devices. The spin Seebeck effect has been investigated extensively over the last few years, but only a little is known about its behaviour near the magnetic phase transition.

Using a stochastic model established through the study of dynamic critical phenomena, the authors have investigated the behavior of the spin Seebeck effect near the Curie temperature Tc of a simple ferromagnet which is composed of a single sublattice such as EuO. They have clarified theoretically that the spin Seebeck signal scales with the magnetization, i.e., ~(T-Tc)1/2. Because no corresponding experiments have been reported so far, the theoretical prediction awaits experimental proof.

H. Adachi, Y. Yamamoto and M. Ichioka, Spin Seebeck effect in a simple ferromagnet near Tc: a Ginzburg–Landau approach, J. Phys. D: Appl. Phys. 51, 144001 (2018)
[Abstract]