Electron spin resonance and magnetic characterization of theGd5.09Ge2.03Si1.88

Abstract

Electron spin resonance was applied on samples of Gd 5.09 Ge 2.03 Si 1.88 . The results are discussed under the scope of magnetization measurements, optical metallography, and wavelength dispersive spectroscopy. Polycrystalline arc-melted samples submitted to different heat treatments were investigated. The correlation of the electron spin resonance and magnetization results permitted a characterization of the present phases and their transitions. Two coexisting phases in the temperature range between two phase transitions have been identified and associated to distinct crystallographic phases. Additionally, the magnetic moment at high temperatures has been estimated from the measured effective g factor. A peak value of 21.5 J / kg K for the magnetocaloric effect was obtained for a sample heat treated at 1500°C for 16 h.

Coupled magnetostructural transformations in melt-spun Ni55Mn19.6Ga25.4 ribbon: An electron spin resonance study

“…The weak temperature dependence of H res and the Dysonian line shape indicate a typical paramagneticlike behavior. 13 Corroborating the above results with thermal and magnetization studies, the observed H res in the high temperature regime corresponds to paramagnetic austenite ͑PA͒ phase.…”

Powder metallurgy influences on the magnetic properties of Gd5.09Ge2.03Si1.88 alloy

“…A second-order magnetic transition appears around 300 K, and in this transition the MCE is negligible when compared to the MCE calculated for the first-order transition [4]. When the T c is close to room temperature, the material becomes a good candidate for application in domestic magnetic refrigeration systems.…”

“…The samples were characterized by magnetic analysis and the results have shown an intense first-order transition (typical for the Gd 5 Ge 2 Si 2 monoclinic phase) at 266 K and a small second-order transition (typical for the Gd 5 Si 4 orthorhombic phase) at 300 K for the as-cast bulk samples [4].…”

“…For the Gd 5 (Ge x Si 1Àx ) 4 alloys the GMCE occurs when a magnetic change (ferromagnetic/paramagnetic) occurs simultaneously with a structural change (monoclinic/orthorhombic) around the Curie temperature (T c ), which results in a relatively high isothermal entropy variation (DS T ) [2].…”

Photoacoustic based technique for measuring the magnetocaloric effect

“…It is common, however, the formation of other phases than the one with the nominal stoichiometry, with phase transitions occurring in temperatures relatively close to each other. Usually one of the transitions is of first order type and the other is of second order type [3]. …”