Lanthanum Dilution Effects on the Giant Magnetocaloric Gd₅Si_1.8Ge_2.2 Compound

Abstract

A study on the fundamental properties of Gd 5Àx La x Si 1.8 Ge 2.2 pseudo-binary compounds with x ¼ 1, 2, 3, 4, and 5 is performed by means of X-ray powder diffraction (XRD) and magnetic measurements. An evolution from a monoclinic (M) Gd 5 Si 2 Ge 2 -type to a tetragonal (T) Zr 5 Si 4 -type structure, with the addition of La, is observed, finding that the T phase is stable for x ! 2. A monotonic expansion of the unit cell volume with a rate of 28 Å3/La by increasing the content of the non-magnetic La ions in the system influences significantly the overall magnetic behavior. For instance, T C decreases in a rate of dT C /dx ¼ À47.8 K La À1 ; and a considerable hysteresis reduction is observed as a result of the change on the nature of the phase transition from a first to a second-order one. Hence, these results reveal the impact of a non-magnetic La substitution on both magnetic and crystallographic properties of this series.

Freestanding and flexible composites of magnetocaloric Gd5(Si,Ge)4 microparticles embedded in thermoplastic poly(methyl methacrylate) matrix

“…The strong spin-lattice coupling on the Gd 5 (Si,Ge) 4 family compounds allows the use of its magnetic results to infer the crystallographic phases fractions 25 . Above the ferroparamagnetic temperature transition, the magnetic susceptibility is described by the Curie-Weiss law where we should consider the amount of each phase x on the sample as follows 38 :…”

Evolution of two-step magnetic transition on nanogranular Gd5Si1.3Ge2.7 thin film

“…The GMCE results from the strong spin lattice coupling present in these materials, which leads to magnetostructural transitions with large heat release or absorption (when magnetic field is applied or removed, respectively) [8]. Their transition temperature can be adjusted by substituting the rare earth element or by tuning the Si, Ge concentration (x) [9][10][11]. Despite the remarkable MCE, their large magnetic hysteresis combined with the heavy rare-earths increasing prices constitute an effective limitation on the scale-up processing of these materials.…”