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Magnetic properties, magnetocaloric effect, and critical behavior of Fe84-xCr2+xB2Co2Zr10 (x = 1, 2, 3, 4, 5, and 6) rapidly quenched alloy ribbons prepared by melt-spinning method have been investigated. X-ray diffraction analysis shows that the ribbons are almost amorphous. All the ribbons exhibit soft magnetic behavior with a low coercivity, Hc < 20 Oe. The magnetic phase transition temperature of the alloy can be adjusted in the room temperature region by appropriate Cr concentrations. With increasing Cr concentration, Curie temperature (TC) of the alloys is reduced from 330 K (for x = 1) to 290 K (for x = 6). The quite high maximum magnetic entropy change, |ΔSm|max > 0.8 J.kg−1.K−1 (under a magnetic field change of 12 kOe), and the wide working temperature range, δT > 90 K, around room temperature, have been achieved on these alloy ribbons. The obtained results reveal that Fe84-xCr2+xB2Co2Zr10 alloys are potential candidates for the magnetic refrigerants at room temperature region. Using the Arrott-Noakes method, critical analyses around the ferromagnetic-paramagnetic phase transition elucidated the magnetic orders in the alloys. The critical parameters determined for Fe84-xCr2+xB2Co2Zr10 ribbons are close to those of the mean-field theory applied for the long-range ferromagnetic orders. [ABSTRACT FROM AUTHOR]

[Display omitted] • A submillimeter-scale microchannel/pillar structure composed of La(Fe,Si) 13 compound was fabricated by reactive sintering using an NaCl mold. • Strong first-order magnetic transition was observed in the sintered structures, resulting in a magnetic entropy change of −19 J/kg K. Herein, as the fabrication of the microchannels for fluid flow using La(Fe,Si) 13 magnetic refrigerant material is required while maintaining its superior magnetocaloric performance, sinter molding of the microchannel-designed La(Fe,Si) 13 was investigated using a dissolutive mold comprised of NaCl to develop a molding process without contamination by carbon and other light elements. In addition, to avoid the thermal decomposition of fine particles of La(Fe,Si) 13 , a solid-state reaction was conducted during sintering using a mixture of α-Fe and La-rich compounds as the initial powder. After sintering, the sample shape exhibited channel widths and depths of 200 μm and pillar widths of 300 μm, which were originally designed for the NaCl dissolutive mold. The metallographic microstructure mostly comprised the La(Fe,Si) 13 phase, and the volume fractions of the extra phases, such as α-Fe and La 2 O 3 , were suppressed to 1.1 % and 3.2 %, respectively. The maximum of the magnetic entropy change in a single pillar reached −19 J/kg K. Direct observation of magnetic nucleation/growth confirmed the smooth emergence of the first-order transitions in multiple pillars. Consequently, this fabrication approach promoted micro-channel-designed La(Fe,Si) 13 H y while maintaining a large magnetocaloric effect via low carbon contamination. [ABSTRACT FROM AUTHOR]

Highlights: [•] The single-phase formation process of La(Fe0.89Si0.11)13 was investigated. [•] The NaZn13-type single-phase is obtained by annealing for 300h at 1323K. [•] The Curie temperature is increased by annealing due to compositional homogenization. [•] The isothermal magnetic entropy change was related to the microstructure. [•] The peak position of the isothermal magnetic entropy change is affected by annealing. [Copyright &y& Elsevier]

The magnetocaloric properties of new complex magnetic material LaSrCuMnO, suitable for the Ericsson cycle, have been investigated. For this material, the effect of Cu doping can be attributed to a combination of doping disorder, Cu-Mn super exchange interactions and a site-percolation mechanism, which suppress the metallic conduction and Curie temperature. The Curie temperature decreases to 355 K. The magnetocaloric study exposes a comparable value of the magnetic entropy change for LaSrCuMnO sample, the value of the maximum entropy change, increases from 1.132 J/kgK to 3.11 J/kgK as magnetic field increases from 1 T to 4 T. A large relative cooling power ( RCP) has been observed for LaSrCuMnO As a result, the studied sample can be considered as potential material for magnetic refrigeration. [ABSTRACT FROM AUTHOR]

Abstract: The effect of Ti substitution on the magnetocaloric effect of the La0.70Sr0.30MnO3 perovskite was investigated. The magnetic entropy change (−ΔS M ) was deduced by two methods: a Maxwell relation and the Landau theory. The magnetocaloric data displays a large value of the magnetic entropy change (−ΔS M ) near the Curie temperature (T C =210K), which increases when increasing the applied magnetic field. A good agreement is found between the experimental (−ΔS M ) and the one estimated by Landau theory. The relative cooling power values vary from 49 to 288Jkg−1 upon variation of the applied magnetic field at 1 and 5T. Under 5T, the relative cooling power value for La0.70Sr0.30Mn0.90Ti0.10O3 is about 70% of the conventional refrigerant Gd material. As a result, the herein reported compound can be considered as a promising material in magnetic refrigeration technology. [Copyright &y& Elsevier]

Abstract: The rare earth mononitride, ErN, has been synthesized by the carbothermic reduction and hot isostatic press methods. The magnetocaloric effect of ErN has been evaluated by calculating the magnetic entropy changes, ΔS, from the magnetization data sets and from the heat capacity measured at various temperatures and applied fields. The two results are in good agreement with each other. The ΔS value of ErN is the highest at 7.5K and higher than that of ErNi2 reported as the candidate material for the magnetic refrigerant of cryogenic technology. Heat capacity curve against temperature of ErN has a peak at 4.4K at zero-field. The peak value of the heat capacity of ErN is 507kJK−1 m−3. This value is larger than those of Er3Ni used commercially as a magnetic regenerator for the Gifford–McMahon refrigerator. The present results indicate that ErN is a promising material for the magnetic refrigerant and regenerator of cooling systems working above the boiling temperature of helium. [Copyright &y& Elsevier]

Single-crystal X-ray diffraction analysis revealed that the central core of the cluster {ZnGd 12 } is unprecedented and composed of a beautiful structure built by two monocapped triangular prisms [ZnGd 6 sharing the ZnII vertex. Magnetic studies reveal that the magnetic field entropy of {ZnGd 12 } in a magnetic field of 7 T–2 T is 30.79 J kg−1 K−1. • A nanoscopic cluster {ZnGd 12 } have been synthesized based on ligand H 2 L. • The cluster {ZnGd 12 } has two monocapped triangular prisms [ZnGd 6 sharing ZnII vertices. • The −Δ S m of {ZnGd 12 } is 30.79 J kg−1 K−1. A novel tridecanuclear nanoscopic cluster {ZnGd 12 } have been synthesized by using the Schiff-base ligand, 2-methoxy-6-[(2-methylindole-2-carboxyl-1-ylidene) methyl]phenol (H 2 L), with zinc chloride and gadolinium nitrate in the presence of triethylamine as deprotonation reagent. Single-crystal X-ray diffraction analysis revealed that the central core of the cluster {ZnGd 12 } is unprecedented and composed of a beautiful structure built by two monocapped triangular prisms [ZnGd 6 sharing the ZnII vertex. Magnetic studies reveal that {ZnGd 12 } shows promise as a low-temperature magnetic refrigerant with the magnetic field entropy of 30.79 J kg−1 K−1 at a magnetic field of 7 T–2 T. [ABSTRACT FROM AUTHOR]