Experimental Study and Development of Rare Earth Iron Garnets as Pure Spin-Current Sources
Abstract
The advent of spintronics in 1988 represents a step forward in the development of high efficiency electronics. Adding the spin degree of freedom allows the design of new technologies that do not require charge motion in a device, which translates in lower energy dissipation, for this reason ferromagnetic insulators have played an important role in the research of new spintronic applications.
Rare earth iron garnets are a type of ferromagnetic insulators which physical and chemical characteristics make them the ideal candidates for their use in spintronic research, for this reason is of great importance to understand their properties to exploit them to their full potential.
The first chapter covers an introduction to spintronics and iron garnets as candidates for their application on the development of new technologies, the basic concepts of spintronics are covered in this section.
In chapter two it is covered the concept of magnetic anisotropy and its control by thickness dependence in iron garnet thin films. Here, it is demonstrated that by exerting an adequate strain in the lattice structure of the iron garnet it is possible to align its magnetization perpendicular to the sample plane, and that the magnitude of this effect can be systematically tuned by the thickness of the iron garnet thin film. The obtention of this perpendicular magnetic anisotropy is an important requirement for the study of physical phenomena such as Quantum Anomalous Hall Effect.
In chapter three the effect of lattice strain in the dynamic magnetic properties of europium iron garnet are analyzed. The strain on the films is applied by lattice mismatch by the use of different garnet substrates, and then subsequently studied by ferromagnetic resonance technique, which provides important information about the dynamics of spin wave propagation. In this experiment, it was found that the intrinsic damping, which is associated to the energy dissipation of a spin wave, is independent of the lattice strain.
Finally, in chapter four the use of iron garnets as a source of pure spin-current is examined. By setting up spin Seebeck effect and spin pumping experiments, the spin wave transmission through different configurations and posterior charge conversion on materials with large spin-orbit coupling are studied.