Giant magnetocaloric effect in Co2FeAl Heusler nanoalloy at high temperature (original) (raw)
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arXiv: Strongly Correlated Electrons, 2019
We have synthesized A2 disordered Heusler nanoalloy and observed giant magnetocaloric effect during the magnetic field induced magneto structural phase transition (MST). The magnetic entropy change shows a positive anomaly at 1252 K. The entropy change is increased linearly with magnetic field and a large value of ~15 J/Kg is detected under a moderate field of 1.4 T near the magneto-structural phase transition temperature (Tt). It leads to a net relative cooling power of 89 J/Kg for the change of magnetic field of 1.4 T. The Arrott plot explores the essential information of the nature of MST. This giant magnetocaloric effect is anticipated to be incorporated in magnetic refrigeration that will not only be an alternative of energy saving but also eco-friendly.
Giant magnetocaloric effect in Co2FeAl Heusler alloy nanoparticles
Journal of Physics D: Applied Physics
A giant magnetocaloric effect across the ferromagnetic (FM) to paramagnetic (PM) phase transition was observed in chemically synthesized Co2FeAl Heusler alloy nanoparticles with a mean diameter of 16 nm. In our previous report, we have observed a significant enhancement in its saturation magnetization (Ms) and Curie temperature (Tc) as compared with the bulk counterpart. Motivated from those results, here, we aim to explore its magnetocaloric properties near the Tc. The magnetic entropy change (−∆) shows a positive anomaly at 1252 K. −∆ increases linearly with the magnetic field, and a large value of ~15 J/Kg-K is detected under a moderate field of 14 kOe. It leads to a net relative cooling power of 89 J/Kg for the magnetic field change of 14 kOe. To confirm the nature of magnetic phase transition, a detailed study of its magnetization is performed. The Arrott plot and nature of universal curve conclude that FM to PM phase transition in the present system is of second-order.
Structural, magnetic, and magnetocaloric properties of Fe2CoAl Heusler nanoalloy
Journal of Magnetism and Magnetic Materials
Spherical nanoparticles (NPs) of size 14±7 nm, made of intermetallic Fe2CoAl (FCA) Heusler alloy, are synthesized via the co-precipitation and thermal deoxidization method. X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns confirm that the present nanoalloy is crystalized in A2-disordered cubic Heusler structure. Magnetic field (H) and temperature (T) dependent magnetization (M) results reveal that the NPs are soft ferromagnetic (FM) with high saturation magnetization (Ms) and Curie temperature (Tc). Fe2CoAl nanoalloy do not follow the Slater Pauling (SP) rule, possibly because of the disorder present in the system. We also investigate its magnetic phase transition (MPT) and magnetocaloric (MC) properties. The peak value of −∆SM (entropy change) vs T curve at a magnetic field change of 20 kOe corresponds to about 2.65 J/kg-K, and the observed value of refrigeration capacity (RCP) is as large as 44 J/kg, suggesting a large heat conversion in magnetic refrigeration cycle. The Arrott plot and the nature of the universal curve accomplish that the FM to paramagnetic (PM) phase transition in Fe2CoAl nanoalloy is of second-order. The present study suggests that the Fe2CoAl nanoscale system is proficient, useful
Structural , magnetic , and magnetocaloric properties of intermetallic Fe 2 CoAl Heusler nanoalloy
2021
Spherical nanoparticles (NPs) made of intermetallic Fe2CoAl (FCA) Heusler alloy are synthesized via co-precipitation method and its structural, magnetic and magnetocaloric properties are explored, for the first time. The basic structural characterizations have revealed A2-disordered cubic Heusler structure. HRTEM with the SAED pattern analysis revealed crystalline nature of the FCA-NPs with a mean diameter of around 14 nm. Field and temperature dependent magnetization (M) study shows that the NPs are soft ferromagnetic with a high saturation magnetization (Ms) and Curie temperature (Tc). We also observed that FCA-NPs do not follow the Slater Pauling (SP) rule possibly because of the disorder present in this system. We further investigate its phase transition and magnetocaloric properties. The peak value of -∆SM vs T curve at a magnetic field change of 20 kOe corresponds to about 2.65 J/Kg-K, and the observed value of refrigeration capacity (RCP) was as large as 44 J/Kg, suggesting a...
Phase Transitions, 2019
The structural measurement indicates that the system possesses A2 to B2 phase transformation at the extent of A2 phase at room temperature. The present system shows first order magneto-structural transformation (FOMST). The substitution of Cr by Fe causes a vital role for an increase in magnetocaloric properties. The change in magnetic entropy (ΔS M) and relative cooling power (RCP) are evaluated under an applied field of 20 KOe that shows drastic changes near the blocking temperature under the specific temperature regime. In the vicinity of these observed properties, critical exponent parameters such as, β, Y and δ were also observed using field dependence magnetic entropy change.
Magnetic anisotropies and magnetization reversal of the Co2Cr0.6Fe0.4Al Heusler compound
Journal of Applied Physics, 2006
Magnetic anisotropies and magnetization reversal properties of the epitaxial Heusler compound Co 2 Cr 0.6 Fe 0.4 Al (CCFA) deposited on Fe and Cr buffer layers are studied. Both samples exhibit a growth-induced fourfold anisotropy, and magnetization reversal occurs through the formation of stripy domains or 90 • domains. During rotational magnetometric scans the sample deposited on Cr exhibits about 2 • sharp peaks in the angular dependence of the coercive field, which are oriented along the hard axis directions. These peaks are a consequence of the specific domain structure appearing in this particular measurement geometry. A corresponding feature in the sample deposited on Fe is not observed.
Magnetic microstructure and magnetotransport in Co2FeAl Heusler compound thin films
Applied Physics Letters, 2011
We correlate simultaneously recorded magnetotransport and spatially resolved magneto-optical Kerr effect ͑MOKE͒ data in Co 2 FeAl Heusler compound thin films micropatterned into Hall bars. Room temperature MOKE images reveal the nucleation and propagation of domains in an externally applied magnetic field and are used to extract a macrospin corresponding to the mean magnetization direction in the Hall bar. The anisotropic magnetoresistance calculated using this macrospin is in excellent agreement with magnetoresistance measurements. This suggests that the magnetotransport in Heusler compounds can be adequately simulated using simple macrospin models, while the magnetoresistance contribution due to domain walls is of negligible importance.
Structural, magnetic and transport properties of Co2FeSi Heusler films
Here we present and discuss structural, magnetic and transport properties of the new ternary cage compound Ce 4 Pd 12 Sn 25 . The isostructural Pt analogue, Ce 4 Pt 12 Sn 25 has previously been characterized as a metallic Kondo lattice system with a very low Kondo temperature T K ≈ 0.25 K and an antiferromagnetic ground state with a Néel temperature T N = 0.19 K. In contrast to the expectations that the smaller unit cell volume of Ce 4 Pd 12 Sn 25 compared to Ce 4 Pt 12 Sn 25 will weaken the magnetism and tune the system closer to a magnetic instability, we found evidence for a phase transitions at a higher temperature T mag = 0.265 K.
Giant Room-Temperature Magnetocaloric Effect Across the Magnetostructural Transition in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mo stretchy="false">(mml:mrowmml:miMnmml:miNimml:miSi<mml...
Physical review applied, 2020
Magnetic and structural transitions are observed to coincide at around room temperature in transitionmetal-based (MnNiSi) 1-x (FeCoGa) x (x = 0.15 and 0.16) alloys, which leads to a coupled first-order magnetostructural transition (MST) from paramagnetic hexagonal to ferromagnetic orthorhombic structure, and, as a result, a giant magnetocaloric effect is observed in these alloys. With subsequent doping for x = 0.17, the MST decouples into two separate transitions, structural and magnetic, although the transitions couple upon enhancing the applied magnetic field. The alloys with x = 0.15, 0.16, and 0.17 are found to exhibit isothermal magnetic entropy changes (| S M |) as large as about 25 J kg −1 K −1 at 323 K, about 31.1 J kg −1 K −1 at 281 K, and about 23.8 J kg −1 K −1 at 213 K, respectively, due to a field change of H = 50 kOe. These low-cost materials may be considered as promising candidates for magnetic refrigeration around room temperature due to their giant magnetocaloric properties, with significantly large relative cooling power (