Spin and magnon transport in antiferromagnetic van der Waals materials and yttrium iron garnet

In this thesis, we have studied the properties of yttrium iron garnet (YIG) and antiferromagnetic
van der Waals materials via spin currents. Devices were fabricated on top of
these materials to study magnon transport in these materials using a nonlocal geometry.
Furthermore, the interaction of a spin current, generated in a heavy metal, with the top
layers of the magnets were studied to characterize the magnetization texture.

The magnetic materials studied in thesis are insulators, and therefore, the spins are
not transported via conducting electrons but via spin waves, called magnons. Magnons
are the quantized representation of the magnetic excitation of a magnetically ordered
system. In this thesis, we have excited them electrically and thermally.

The majority of the magnetic materials studied in this thesis are antiferromagnetic van der Waals materials. In antiferromagnets all magnetic moments order antiparallel to each other, and therefore, the net magnetic moment is zero. Antiferromagnetic materials have recently gained great interest for information storage and as a medium for spin currents in spintronic devices. Van der Waals materials consist of crystal layers which are weakly bonded to each other via van der Waals interactions whereas within the layers the atomic bonds are much stronger.

Magnon transport is characterized in these materials and the spin structures of these materials are studied via spin Hall magnetoresistance measurements. We have shown that we can modulate the magnon transport via the injection of magnons via permalloy strips . Furthermore the spin-flop transition is detected via thermally generated magnons.