Irrecoverable and Recoverable Resistivity Resulting From the First Order Magnetic-Structural Phase Transition in Gd<formula formulatype="inline"> <tex Notation="TeX">$_5$</tex></formula>(Si<formula formulatype="inline"> <tex Notation="TeX">$_x$</tex></formula>Ge<formula formulatype="inline"><tex Notation="TeX">$_{1-x}$</tex></formula>)<formula formulatype="inline"><tex Notation="TeX">$_4$</tex></formula>

Abstract

An irreversible change in resistivity occurs in Gd 5 (Si x Ge 1−x ) 4 at the first-order phase transformation each time the material is cycled through its transition. This results in a progressive increase in resistivity each time the material is cycled through the transition and returned to its initial conditions of temperature and magnetic field. The effect of a first-order magnetic/structural phase transition on the resistivity of a material, and its recovery by annealing have not been reported before, and consequently, there has been no theoretical analysis of the effect until now. We postulate that if the material is held at an elevated temperature, the resistivity recovers and recovery time decreases with temperature. A model has been developed to explain the recovery in resistivity when the sample is held at elevated temperatures over a period of time and this has been verified experimentally.Index Terms-Coupled phenomena, magnetoresistance, resistivity recovery, magentocaloric effect, first-order structural phase transition.

Growth and characterisation of Gd5(SixGe1−x)4 thin film

“…2 Bruck et al reported giant magnetocaloric effect in non-rare earth materials (MnFeP 0.45 As 0.55 ) at room temperature. 3 There has been extensive work on bulk magnetocaloric materials [1][2][3][4][5][6][7] but there are fewer reports on thin films or other nanostructured magnetocaloric materials, although thin films of magnetocaloric materials have potential applications in micro-cooling in ICs and MEMS. Sambandam et al 8 reported unsuccessful growth of Gd 5 Si 2 Ge 2 thin film at a higher temperature of 750-1150 C using sputtering technique on a silicon nitride wafer.…”

Second order phase transition temperature of single crystals of Gd5Si1.3Ge2.7 and Gd5Si1.4Ge2.6

“…These estimated second order phase transition temperatures are significantly higher than the transition temperatures of sample with compositions 0.375 < x < 0.51, which may be due to presence of the orthorhombic I phase in the samples. In addition, one can also see that the transition temperature increases with decreasing amount of Si for this phase as opposed to the Si-rich region of Gd 5 (Si x Ge 1Àx ) 4 . In the mixed phase region of the phase diagram of Gd 5 (Si x Ge 1Àx ) 4 , single crystal sample of Gd 5 Si 1.5 Ge 2.5 obeys the modified Arrott plot technique to determine the "hidden" second order phase transition temperature of the orthorhombic II and monoclinic phases 10 but not the compositions of Gd 5 Si 1.3 Ge 2.7 and Gd 5 Si 1.4 Ge 2.6 as shown in Fig.…”

“…Second order phase transition temperature of single crystals of Gd 5 4 still remains a magnetocaloric material of great interest due to its giant magnetocaloric effect near room temperature. The material has been widely studied over the composition range 0.41 < x < 0.51, where the coupled magnetic and structural first order phase transitions occur close to room temperature.…”

“…The material has been widely studied over the composition range 0.41 < x < 0.51, where the coupled magnetic and structural first order phase transitions occur close to room temperature. [1][2][3][4][5] Gd 5 (Si x Ge 1Àx ) 4 has a mixed phase region in the phase diagram with both Sm 5 Ge 4 type (orthorhombic I) and Gd 5 Si 4 type (orthorhombic II) phases for compositions 0.32 < x < 0.41. 6 There has been little research on specific composition in this region.…”