Mössbauer spectroscopic evaluation of chemical and electronic distributions in La(Fe0.81Si0.19)13

Hamdeh, Hussein H.; Al-Ghanem, H.; Hikal, Walid M.; Taher, S. M. A.; Ho, J. C.; Anh, Do Thi Kim; Thuy, N.P.; Duc, Nguyen Huu; Pham, Thang

doi:10.1016/j.jmmm.2003.07.004

Cited by 33 publications

(12 citation statements)

References 13 publications

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“…Table summarizes the parameters fitted to the Mössbauer spectra at different temperatures. The parameters of each phase are in general agreement with literature data. ,, For example, the hyperfine field of the Si-poor phase at 180 K is close to that reported for LaFe 11.7 Si 1.3 at 184 K (24.5 vs 23.5 T) and the hyperfine field of the Si-rich phase at 200 K falls between those reported for LaFe 11.6 Si 1.6 and LaFe 11.4 Si 2.0 . Here, attention is focused on the parameters of the Si-rich and the Si-poor phase at 180 K and lower temperatures.…”

Section: Resultssupporting

confidence: 86%

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Nanoscale Phase Separation and Large Refrigerant Capacity in Magnetocaloric Material LaFe_11.5Si_1.5

Huang

Brown

et al. 2021

Chem. Mater.

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Ferromagnetic transitions, the magnetocaloric effect, and the atomic-scale microstructure in an annealed bulk material of LaFe 11.5 Si 1.5 were investigated using magnetic measurements, Mossbauer spectroscopy, high-resolution X-ray diffraction analysis, and high-resolution transmission electron microscopy. The results provide evidence of the coexistence of two ferromagnetic phases with different Curie temperatures. The phase with a Curie temperature of 216 K corresponds to a Sirich phase of a NaZn 13 -type structure with a small lattice volume, whereas the phase with a Curie temperature of 185 K corresponds to a Si-poor phase of a NaZn 13 -type structure with a large lattice volume. This phase coexistence is observed on a nanometer scale and it can account for inverse thermal hysteresis of the ferromagnetic transition in the Si-rich phase during warming. Furthermore, the phase coexistence helps the bulk material achieve a refrigeration capacity of 170 J kg −1 due to a combination of the magnetocaloric effect in each phase. It is determined that the magnetocaloric effect in the Si-rich and the Si-poor phase brings about a maximum of the total entropy change of −3.55 and −6.80 and J kg −1 K −1 at respective Curie temperatures, respectively. Fundamentally, the phase coexistence indicates coloring of Si atoms in the lattice of a NaZn 13 -type structure and can be attributed to nanoscale phase separation of a disordered precursor during annealing of the bulk material. The nanoscale phase separation may occur in other magnetocaloric materials, thus allowing for improvement of their refrigeration capacity.

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Section: Resultssupporting

confidence: 86%

“…In contrast, the hyperfine field of the Si-poor phase is about 10% larger. These differences suggest that Fe atoms have different valence states in the two phases . The quadrupole splitting and the line width of the Si-poor phase are larger than those of the Si-rich phase.…”

Section: Resultsmentioning

confidence: 92%

Nanoscale Phase Separation and Large Refrigerant Capacity in Magnetocaloric Material LaFe_11.5Si_1.5

Huang

Brown

et al. 2021

Chem. Mater.

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“…From a neutron diffraction experiment, Wang et al [22] concluded that Si is randomly distributed between the 8b and the 96i sites. A very different conclusion was drawn from the analysis of 57 Fe Mö ssbauer spectra [23]: the Si atoms occupy the 96i sites only. The latter result is in agreement with an earlier neutron study of an isomorphous compound LaFe 13Àx Al x [24], where the same strong preference of Al for the 96i sites was found.…”

Section: -Type Compoundsmentioning

confidence: 93%

La(Fe,Si)13-based magnetic refrigerants obtained by novel processing routes

Lyubina

Gutfleisch

Kuz’min

et al. 2008

Journal of Magnetism and Magnetic Materials

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a b s t r a c tThe structure and magnetic properties of LaFe 13Àx Si x and Co-substituted LaFe 11.8Àx Co x Si 1.2 alloys prepared by melt spinning, as well as of LaFe 11.57 Si 1.43 H x hydrides prepared by reactive milling are investigated. The hysteresis in the temperature-and field-induced phase transitions is significantly reduced as compared with conventional bulk alloys, which makes these materials very attractive for magnetic refrigerant applications. The unusual combination of features characteristic of first-and second-order phase transitions in the La(Fe,Si) 13 -based compounds is discussed on the basis of densityfunctional electronic structure calculations.

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“…[4,17,21,[62][63][64] La(Fe x Si 1Àx ) 13 crystallizes in ar ather complex cubic NaZn 13 (Fm3 m) structure with 112 atoms in the unit cell and two inequivalent Fe sites.F e I resides on 8b sites,l ocatedi nt he center of icosahedral cages formed by Fe II on the 96i sites. These sites are shared with Si, which is required to stabilize the structure.L ai sp ositioned on the 8a sites [65][66][67] as depicted in Figure2.F or the composition LaFe 11.6 Si 1.4 ,w hich we used for our experiments,the magnetostructural transition was observed to be approximately T t % 190 K. In our samples we observed an arrow,b ut noticeable thermal hysteresis of 3K. [25,35] Thet ransition from the ferromagnetic (FM) to the paramagnetic (PM) phase is accompanied by as ignificant volume decreaseo f% 1%, [68] but the lattice symmetry remains the same.T his leads to interface and volumetric stress during the transition, whichi sapotential cause of hysteresis.…”

Section: Disentangling the Microscopic Contributions To The Entropy Cmentioning

confidence: 99%

Hysteresis Design of Magnetocaloric Materials—From Basic Mechanisms to Applications

et al. 2018

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Magnetic refrigeration relies on a substantial entropy change in a magnetocaloric material when a magnetic field is applied. Such entropy changes are present at first‐order magnetostructural transitions around a specific temperature at which the applied magnetic field induces a magnetostructural phase transition and causes a conventional or inverse magnetocaloric effect (MCE). First‐order magnetostructural transitions show large effects, but involve transitional hysteresis, which is a loss source that hinders the reversibility of the adiabatic temperature change ΔTad. However, reversibility is required for the efficient operation of the heat pump. Thus, it is the mastering of that hysteresis that is the key challenge to advance magnetocaloric materials. We review the origin of the large MCE and of the hysteresis in the most promising first‐order magnetocaloric materials such as Ni–Mn‐based Heusler alloys, FeRh, La(FeSi)13‐based compounds, Mn3GaC antiperovskites, and Fe2P compounds. We discuss the microscopic contributions of the entropy change, the magnetic interactions, the effect of hysteresis on the reversible MCE, and the size‐ and time‐dependence of the MCE at magnetostructural transitions.

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Mössbauer spectroscopic evaluation of chemical and electronic distributions in La(Fe0.81Si0.19)13

Cited by 33 publications

References 13 publications

Nanoscale Phase Separation and Large Refrigerant Capacity in Magnetocaloric Material LaFe_11.5Si_1.5

Nanoscale Phase Separation and Large Refrigerant Capacity in Magnetocaloric Material LaFe_11.5Si_1.5

La(Fe,Si)13-based magnetic refrigerants obtained by novel processing routes

Hysteresis Design of Magnetocaloric Materials—From Basic Mechanisms to Applications

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Mössbauer spectroscopic evaluation of chemical and electronic distributions in La(Fe0.81Si0.19)13

Cited by 33 publications

References 13 publications

Nanoscale Phase Separation and Large Refrigerant Capacity in Magnetocaloric Material LaFe11.5Si1.5

Nanoscale Phase Separation and Large Refrigerant Capacity in Magnetocaloric Material LaFe11.5Si1.5

La(Fe,Si)13-based magnetic refrigerants obtained by novel processing routes

Hysteresis Design of Magnetocaloric Materials—From Basic Mechanisms to Applications

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Nanoscale Phase Separation and Large Refrigerant Capacity in Magnetocaloric Material LaFe_11.5Si_1.5

Nanoscale Phase Separation and Large Refrigerant Capacity in Magnetocaloric Material LaFe_11.5Si_1.5