Efeito magnetocalorico em filmes finos nanocompositos sintetizados por sputtering / Magnetocaloric effect in nanocomposite thin films obtained by sputtering

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

The magnetic properties of films obtained by the co-deposition of a ferromagnetic and a non-magnetic components are the subject of intense investigation. In this work, the magnetic properties of Gdx W1-x, with x ranging from 0 to 1, were investigated. The films were deposited by magnetron sputtering from Gd and W targets. EPMA (electron probe microanalysis) and low-angle XRD (x-ray diffraction) were used to determine the film atomic composition and structure, respectively. The magnetic moment, m , of the films was measured as a function of temperature, T, and applied field H, using a SQUID (superconducting quantum device) magnetometer. The films were amorphous for 0.15 T B the samples were paramagnetic. TB-values occurred at low temperatures (between 5 K and 50 K). The Curie paramagnetic temperature, deduced from the x -1 vs T plots, where x is the susceptibility, was observed to increase with increasing x. The magnetocaloric effect was investigated from the magnetization isotherms, M vs H, from which the magnetic entropy change, D SM, caused by the application and removal of a 50 kOe field, was deduced. The D SM vs T curves exhibited maxima which varied from 5 K to about room temperature, depending on the Gd concentration

ASSUNTO(S)

gadolinio-tungstenio raios x - difração x rays gadolinium-tungstein superparamagnetism nanoparticles nanoparticulas superparamagnetismo

ACESSO AO ARTIGO

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