Colóquio: Influence of structural deformations and magnetic field deposition on the anisotropy of magnetic thin films (Marcio Medeiros Soares, UFPB)

Ciclo de Colóquios 2024.1

Colóquio #03

“Influence of structural deformations and magnetic field deposition on the anisotropy of magnetic thin films”

Prof. Dr. Marcio Medeiros Soares
Departamento de Física, UFPB.


Sexta-feira, 22 de março de 2024, às 16h, na sala 201


RESUMO
This work explores two original ways to influence the magnetic anisotropy in thin films of interest in spintronics, the deposition under magnetic field and the controlled application of structural deformations. The originality lies in the development of new scientific instrumentation that allow a wide control, either of the application of a magnetic field, or of deformations in thin films deposited on flexible substrates. In addition to effectively influencing the magnetocrystalline anisotropy of thin films, the aim is to understand the mechanisms behind this anisotropy, relating the structure of the films (composition, chemical order, deformations, microstructure) to their electronic and magnetic properties probed by X-ray absorption. We have successfully developed a complex instrument for the application of biaxial deformations in thin films, the biaxial multi analysis strain instrument (2D-MASI), to perform in-situ orientational dependent diffraction (X-ray Stress Analysis) and absorption (X-ray Magnetic Linear Dichroism), as a function of the sample strain state. Such instrumentation fulfilled the portability requirements in X-ray diffraction and absorption beamlines, allowing experiments in high vacuum and low temperature, as well as the deposition of films on pre-tensioned substrates, enabling the study of compressive deformations, in addition to the expansive ones. Although limited in the number of photons in the old UVX source at LNLS, the instrument was able to effectively deform the crystalline structure of thin films (proven by X-ray diffraction), and to influence the magnetic anisotropy of cobalt oxide antiferromagnetic films (probed by Linear Magnetic Dichroism of soft X-rays as a function of temperature). It has already being used at SIRIUS, for coupled diffraction and absorption experiments at the Extreme Conditions beamline (EMA), taking advantage of the enormous gain in beam stability and brightness. We also developed an original instrumentation for the application of a magnetic field during the growth of thin films by sputtering. This instrument has three distinct and simultaneous configurations of magnetic field and allows to apply temperature up to 570 K, using SmCo permanent magnets. An improvement in the thermal insulation of the magnets will allow reaching temperatures of up to 770 K.