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In this report, a successful thermodynamical model was employed to understand the structural transition in Er5Si4, able to explain the decoupling of the magnetic and structural transition. This was achieved by DFT calculations, which were used to determine the energy differences at 0 K, using a LSDA+U approximation. It was found that the M structure is the stable phase at low temperatures, as verified experimentally with a value of ΔF0=-0.262 eV. Finally, a variation of Seebeck coefficient (~6 μV) was determined at the structural transition, which allows to conclude that the electronic entropy variation is negligible in the transition. [ABSTRACT FROM AUTHOR]

The influence of dynamics and sample shape on the magnetic hysteresis in first-order magnetocaloric metamagnetic LaFe13- xSi x with x = 1.4 is studied. In solid-state magnetic cooling, reducing magnetic and thermal hysteresis is critical for refrigeration cycle efficiency. From magnetization measurements, it is found that the fast field-rate dependence of the hysteresis can be attributed to extrinsic heating directly related to the thickness of the sample and the thermal contact with the bath. If the field is paused partway through the transition, the subsequent relaxation is strongly dependent on shape due to both demagnetizing fields and thermal equilibration; magnetic coupling between adjacent sample fragments can also be significant. Judicious shaping of the sample can both increase the onset field of the ferromagnetic-paramagnetic (FM-PM) transition but have little effect on the PM-FM onset, suggesting a route to engineer the hysteresis width by appropriate design. In the field-paused state, the relaxation from one phase to the other slows with increasing temperature, implying that the process is neither thermally activated or athermal; comparison with the temperature dependence of the latent heat strongly suggests that the dynamics reflect the intrinsic free energy difference between the two phases. [ABSTRACT FROM AUTHOR]

A study on the fundamental properties of Gd5−xLaxSi1.8Ge2.2 pseudo‐binary compounds with x = 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) Gd5Si2Ge2‐type to a tetragonal (T) Zr5Si4‐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, TC decreases in a rate of dTC/dx = −47.8 K La−1; 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. A study on the crystallographic, magnetic, and magnetocaloric properties of (Gd,La)5(Si,Ge)4 pseudo‐binary compounds is presented here. The change from a monoclinic to a tetragonal structure for La content higher than 20% is observed. There is a monotonic decrease in TC with a considerable hysteresis reduction and a change on the nature of the phase transition from a first to a second‐order one. [ABSTRACT FROM AUTHOR]

In this report, a successful thermodynamical model was employed to understand the structural transition in Er5Si4, able to explain the decoupling of the magnetic and structural transition. This was achieved by DFT calculations, which were used to determine the energy differences at 0 K, using a LSDA+U approximation. It was found that the M structure is the stable phase at low temperatures, as verified experimentally with a value of ΔF0=-0.262 eV. Finally, a variation of Seebeck coefficient (~6 μV) was determined at the structural transition, which allows to conclude that the electronic entropy variation is negligible in the transition. [ABSTRACT FROM AUTHOR]

The implementation of processed magnetic materials onto thermoplastics can be an approach for practical use of brittle intermetallic materials on device development with the advantage of enlarging the range of applications. In this paper, we present the evaluation on the effect of blending magnetocaloric Gd 5 Si 2.4 Ge 1.6 3.4 μm particles with in different weight fractions onto a flexible, transparent and non-magnetic poly(methyl methacrylate) (PMMA). A close to homogeneous grain distribution along the polymer surface were achieved by using a simple solvent casting method for their magnetocaloric properties studies. From XRD analysis, it was found a unit cell volume shrinkage by increasing the powder concentration followed by a reduction on the amount of secondary monoclinic phase as a result of interfacial interactions. As a consequence, a weakening of secondary phases effect on the composite magnetocaloric behavior is observed as a result of the effective hydrostatic pressure from the difference between thermal expansions of matrix and filler. Unlabelled Image • Particle size reduction of Gd 5 Si 2.4 Ge 1.6 bulk to 3.4 μm increases the detection on the amount of distorted monoclinic phase. • The solvent casting technique allows a close to homogeneous dispersion of the micropowder along the composite volume. • Inclusion of the micropowder into the thermoplastic converts the monoclinic phase into an orthorhombic-I phase. • PMMA matrix works as a pressure cell for the micropowder leading to a reduction on the magnetocaloric response of the monoclinic phase. [ABSTRACT FROM AUTHOR]