Abstract
The effects of Y on the phase composition and magnetocaloric effect in La1−xYxFe11.5Si1.5 compounds were studied. Y2Fe17-type phase and α-Fe phase appear in the annealed La1−xYxFe11.5Si1.5 compounds when x ≥ 0.07 due to small solid solubility of Y in NaZn13 phase. Y2Fe17 phase obstructs the formation of the 1:13 phase, leading to the decrease of magnetic entropy changes. But for x < 0.1, La1−xYxFe11.5Si1.5 compounds exhibit high magnetic entropy changes and low hysteresis loss compared with that of LaFe11.5Si1.5. Consequently, the La1−xYxFe11.5Si1.5 compounds (x < 0.1) are useful to realize large magnetocaloric effect with smaller hysteresis loss.
Highlights
LaFe13−x Six compounds with a NaZn13 -type crystal structure showed first-order magnetic phase transitions at a Curie temperature (TC ), which induced a giant magnetocaloric effect (MCE) when LaFe13−x Six compounds underwent a change from a ferromagnetic state to a paramagnetic state at TC [1]
It indicates that the solid solubility of Y in the 1:13 phase was much smaller compared with Ce and Nd for the annealing compounds [16]
The results show that Y existed in the 1:13 phase and LaFeSi phase for La0.7Y0.3Fe11.5Si1.5 compounds
Summary
LaFe13−x Six compounds with a NaZn13 -type crystal structure (denoted as 1:13 phase) showed first-order magnetic phase transitions at a Curie temperature (TC ), which induced a giant magnetocaloric effect (MCE) when LaFe13−x Six compounds underwent a change from a ferromagnetic state to a paramagnetic state at TC [1]. The peak value of the magnetic entropy change (∆SM ) with temperature variation broadened to just above TC for LaFe13−x Six compounds because of the itinerant-electron magnetic transition [2]. These features make LaFe13−x Six compounds ideal refrigerants for magnetic refrigeration technology [3,4]. LaFe13−x Six compounds display large magnetic and thermal hysteresis due to the first-order nature of their transitions. The developments of the refrigerants with a large magnetic entropy change and small hysteresis losses are still the key for practical applications [7,8].
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