Magnetoelastic effect with Surface Acoustic Waves in Nickel

Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Curs: 2021, Tutor: Ferran Macià BrosSurface acoustic waves (SAW) are micrometric strain waves that propagate on the surface of a solid. They are good for a number of applications and have recently been used for their ability to couple with magnetic states in magnetostrictive materials. In this paper we study the SAW absorption of a magnetic material (Nickel) and find the angle dependence between the SAW propagation direction and the magnetic field orientation. We find that when SAW and the magnetic field are perpendicular or parallel there is no power absorption, but a maximum appears at 45 degrees. Furthermore, there is a dependence with the strength of the magnetic field. At high enough fields the magnetic moments are saturated and have enough energy to overcome the coupling generated by SAW, whereas at lower magnetic fields there is SAW attenuation and a maximum appears at a resonant frequenc

Resonant and Off-Resonant Magnetoacoustic Waves in Epitaxial Fe3Si/GaAs Hybrid Structures

Surface acoustic waves (SAWs) provide an efficient dynamical coupling between strain and magnetization in micro- and nanometric systems. Using a hybrid device composed of a piezoelectric, GaAs, and a ferromagnetic Heusler alloy thin film, Fe3Si, we are able to quantify the amplitude of magnetoacoustic waves generated with SAWs via magnetic imaging in an x-ray photoelectron microscope. The cubic anisotropy of the sample, together with a low damping coefficient, allows for the observation of resonant and nonresonant magnetoelastic coupling. Additionally, via micromagnetic simulation, we verify the experimental behavior and quantify the magnetoelastic shear strain component in Fe3Si, which appears to be large (b2=10±4MJm−3)

Ultracold dipolar bosons trapped in atomtronic circuits

We consider a ring-shaped triple-well potential with few polar bosons characterized by a long-range and anisotropic interaction. By diagonalizing the extended Bose-Hubbard Hamiltonian, that treats sites as macroscopic dipoles, we investigate the ground state properties of the system as we rotate the dipole angle and vary the on-site interaction strength. We find that the competition between dipole and on-site interaction lead to different ground states and that the entanglement between sites depends on the filling factor which can be fractional or integer, and whether the number of particles is odd or even. We further characterize the system by studying the condensed fraction and coherence properties