Spin Seebeck Effect from Antiferromagnetic Magnons and Critical Spin Fluctuations in Epitaxial ${\mathrm{FeF}}_{2}$ Films

Spin Seebeck Effect from Antiferromagnetic Magnons and Critical Spin Fluctuations in Epitaxial ${FeF}_{2}$ Films

Junxue Li, Zhong Shi, Victor H. Ortiz, Mohammed Aldosary, Cliff Chen, Vivek Aji, Peng Wei, and Jing Shi

Phys. Rev. Lett. 122, 217204 – Published 31 May 2019

Abstract

We report a longitudinal spin Seebeck effect (SSE) study in epitaxially grown ${FeF}_{2} (110)$ antiferromagnetic (AFM) thin films with strong uniaxial anisotropy over the temperature range of 3.8–250 K. Both the magnetic-field and temperature-dependent SSE signals below the Néel temperature ( $T_{N} = 70 K$ ) of the ${FeF}_{2}$ films are consistent with a theoretical model based on the excitations of AFM magnons without any net induced static magnetic moment. In addition to the characteristic low-temperature SSE peak associated with the AFM magnons, there is another SSE peak at $T_{N}$ which extends well into the paramagnetic phase. All the SSE data taken at different magnetic fields up to 12 T near and above the critical point $T_{N}$ follow the critical scaling law very well with the critical exponents for magnetic susceptibility of 3D Ising systems, which suggests that the AFM spin correlation is responsible for the observed SSE near $T_{N}$ .

Received 5 January 2019

DOI:https://doi.org/10.1103/PhysRevLett.122.217204

Physics Subject Headings (PhySH)

Antiferromagnetism Magnons Spin current Spintronics

Critical phenomena

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Junxue Li¹, Zhong Shi², Victor H. Ortiz¹, Mohammed Aldosary^1,3, Cliff Chen¹, Vivek Aji¹, Peng Wei¹, and Jing Shi¹

¹Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
²School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
³Department of Physics and Astronomy, King Saud University, Riyadh 11451, Saudi Arabia