Abstract

The combination of the spin transfer torque and spin Hall effects, or their reciprocal dynamical spin pumping and inverse spin Hall effects, respectively, enable reading and controlling the magnetization state in spintronics devices which are at the verge of mass commercialization as the next generation of energy-efficient and fast magnetic random-access memory applications with the use of ferromagnetic elements, e.g., the spin valve. However, these effects have remained elusive in antiferromagnetic-based devices up to date, despite the fascinating advantages offered by the absence of stray fields (zero net magnetization), Terahertz spin dynamics, and the widespread availability of metallic, insulating and semiconducting antiferromagnetic materials. In this thesis I report the first demonstration of sub-Terahertz dynamical spin pumping at the interface between an antiferromagnet and a non-magnetic material; more specifically a uniaxial insulating antiferromagnet MnF2 and heavy metal Pt. The measured ISHE signal generated by the corresponding spin-charge current interconversion in the platinum layer is modulated by the handedness of the circularly polarized sub-THz irradiation. This effect results directly from the opposite chirality of each of the fundamental dynamical modes of the antiferromagnet. Contrary to the case of ferromagnets, this observation in an antiferromagnetic system allows unambiguously differentiating coherent spin pumping from incoherent spin Seeback effect, by which electric signals result from thermal activation. A complete study of the generated electric signals at the antiferromagnetic resonances, the spin-flop mode and the transition between the two regimes as the microwave polarization is continuously varied from circular to linear polarizations enabled an understanding of the different phenomena governing interconversion of spin dynamics and charge currents at the MnF2/Pt interface.

Notes

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Graduation Date

2019

Semester

Fall

Advisor

Del Barco, Enrique

Degree

Doctor of Philosophy (Ph.D.)

College

College of Sciences

Department

Physics

Degree Program

Physics

Format

application/pdf

Identifier

CFE0007870

URL

http://purl.fcla.edu/fcla/etd/CFE0007870

Language

English

Release Date

December 2019

Length of Campus-only Access

None

Access Status

Doctoral Dissertation (Open Access)

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