Enabling Gigantic Antiferromagnetic Spin Caloritronic Effects through Spin Heat Accumulation
Abstract
Major Goals: Our project had four major goals. (1) Develop pump/probe methodologies capable of quantifying spin-polarized heat transfer in magnetic heterostructures on picosecond time scales. (2) Understand how electron-phonon interactions govern transport in magnetic metals. (3) Discover how magnetic properties, especially antiferromagnetic exchange interactions, affect spin caloritronic transport properties. (4) Quantify the interfacial spin Seebeck effect in a metal/antiferromagnetic insulator system. Accomplishments: (1) We developed a pump/probe method capable of independently measuring a metal's electron temperatures, phonon temperatures, and magnetic moment. Our method works by monitoring temperature and magnetism-induced changes in optical properties at wavelengths between 400 and 1000 nm. (2) We used our new pump/probe methodology to explore how composition-induced changes in electronic band structure enable novel magnetic and thermal transport properties in FeCo alloys. We discovered that CoFe alloys have remarkable composition-dependent thermal transport properties. We did not observe evidence that heat-currents are spin-polarized (spin heat accumulation). However, we were able to identify how composition, band structure, and electron-phonon interactions give rise to unique thermal and magnetic properties. (3) We measured the interfacial spin-Seebeck effect in Au/rare-earth iron garnet bilayers. We discovered that the magnitude of the spin Seebeck effect in an Au/iron-garnet system is enhanced by a factor of three by replacing Yttrium with Thulium or Terbium. Replacing Yttrium with Thulium or Terbium modifies the antiferromagnetic exchange interaction between the two antiferromagnetically coupled Fe sublattices in the iron-garnet. By performing wavelength-dependent pump/probe measurements, we discovered that the spin Seebeck effect causes ultrafast demagnetization of the iron garnet layer.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 14, 2021
- Accession Number
- AD1206494
Entities
People
- Richard B Wilson
Organizations
- University of California, Riverside