Banca de DEFESA: MARCUS VINÍCIUS PINHEIRO LOPES

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : MARCUS VINÍCIUS PINHEIRO LOPES
DATE: 26/04/2021
TIME: 09:00
LOCAL: Plataforma Google Meet
TITLE:

Thermoelectric effects in Co2FeAl/W bilayers with uniaxial and cubic anisotropies

KEY WORDS:

Full-Heusler material. Uniaxial and cubic anisotropy. Spin Seebeck effect. Anomalous Nernst effect.

PAGES: 92
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:

The conversion of temperature gradients applied to magnetic materials has been the subject of study for its importance in the possibility of building devices that take advantage of it. The application of these temperature variations generate electrical responses due to the production of spin and charge currents that gave rise to an area of spintronics, the spin caloritronics. From these currents it is possible to measure the thermoelectric voltage in magnetic materials, produced by the direct conversion of the temperature gradient into electrical voltage. In this work, this thermovoltage is mainly associated with two phenomena, the Seebeck spin (SSE) and anomalous Nernst (ANE) effects. Both are investigated in samples of Co2FeAl/W (CFA/W) grown on silicon (Si) and gallium arsenide (GaAs) substrates. The samples were prepared by magnetron sputtering with the substrate under to distinct temperature conditions during deposition, from 300 K up to 773 K. Here, the bilayers were deposited onto oriented substrates in order to induce magnetocrystalline anisotropy, thus allowing the obtainment of systems with an overlap of anisotropies such as uniaxial and cubic. The samples were characterized from the structural and magnetic point of views. Specifically, the structural characterization was performed by X-ray diffractometry (XRD), while the quasi-static magnetic behavior was obtained through magnetization curves measured using a Vibrating Sample Magnetometer (VSM). Thermoelectric response was explored via longitudinal Spin Seebeck effect (LSSE). In this configuration, the temperature gradient is normal to the plane of the film, and the external magnetic field lies in the plane. Then, the thermoelectric voltage is measured with electrical contacts fixed in the film plane. Computer simulations were also carried out using the adapted Stoner-Wohlfarth model, which together with the experimental data show that the thermoelectric response of the samples is the result of the interaction between the uniaxial and cubic contributions of magnetocrystalline anisotropy. The results place CFA grown onto GaAs substrate as a promising candidate for active elements in spintronic devices.

BANKING MEMBERS:
Externo à Instituição - THIAGO JOSÉ DE ALMEIDA MORI - LNLS
Interno - 1508681 - FELIPE BOHN
Presidente - 1474380 - MARCIO ASSOLIN CORREA
Externo ao Programa - 1883170 - MAURICIO ROBERTO BOMIO DELMONTE
Externo à Instituição - MÁRCIO MEDEIROS SOARES - UFPB