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We report the effect of low temperature vacuum annealing (823 K; 550 °C) on the elemental chemical composition, structural phase transition temperatures, phase structure, and magnetic properties of Ni 50.6 Mn 36.3 Sn 13.1 as-solidified ribbons. Their elemental chemical composition, highly oriented columnar-like microstructure and single-phase character (L2 1 -type crystal structure for austenite) remain unchanged after this low temperature annealing. Annealed ribbons show a reduction of interatomic distances which lead to a small change in the characteristic phase transition temperatures (~3–6 K) but to a significant rise of ~73 and 63% in the saturation magnetization of the martensite and austenite phases, respectively, that can be strictly ascribed to the strengthening of ferromagnetic interactions due to the change in interatomic distances. [ABSTRACT FROM AUTHOR]

Abstract: The effect of a severe mechanical milling treatment on the microstructure, magnetic and magneto-caloric properties of Pr2Fe17 powders is reported. Bulk alloys showing a rhombohedral Th2Zn17-type crystal structure were mechanically ball milled under Ar atmosphere. After 10h of milling this crystal structure persists and the mean values of the lattice parameters remain almost unchanged. Average grain sizes around 27nm were estimated by both, transmission electron microscopy and neutron powder diffraction measurements. While for the starting bulk alloys the low field temperature of the magnetization, M(T), shows a well-defined and sharp decrease at the Curie temperature, T C =285(2)K, in ball milled samples the transition becomes broad not allowing an accurate determination of Curie point; in addition, this intrinsic parameter seems to be shifted toward a higher temperature [292(10)K]. The magnetocaloric effect at μ o H max =5T was evaluated from the temperature dependence of magnetic entropy change, through the variation of M(H,T) curves. A decrease in the peak value of magnetic entropy change, , from 5.7 to 3.7Jkg−1 K−1, and the broadening of the maximum is observed for the milled sample respect to the bulk alloy. [Copyright &y& Elsevier]

Abstract: Microstructural and magnetic changes induced by ball milling in Nd2Fe17 alloy have been investigated. X-ray and neutron powder diffraction studies have shown that the main crystalline phase present in the as-cast Nd2Fe17 compound is the rhombohedral Th2Zn17-type crystal structure. Contrary to other materials, the crystal structure does not change after milling, and the crystal lattice parameters slightly increases while the induced strain is less than 0.1%. It has been observed from SEM and TEM images that the microstructure consists of agglomerates of nanoparticles with a mean size around 20nm, and from magnetic measurements a broadening of the temperature range in which ferromagnetic to paramagnetic transition takes place. [Copyright &y& Elsevier]

The crystal structure, and magnetic and magnetocaloric properties of rapidly solidified Ni 0.895 Cr 0.105 MnGe 1.05 melt-spun ribbons is reported. The ribbon samples crystallize into a single-phase hexagonal Ni 2 In-type structure at room temperature. The as-quenched ribbons showed a second order magnetic transition at 192 ± 1 K at μ o H  = 5 mT. A magnetic-field-induced transition from an antiferromagnetic (AFM)-like to a ferromagnetic (FM) state of martensite structure was observed in annealed ribbons below the temperature of the martensitic transformation ( T M  ∼ 245 ± 1 K). The annealed ribbons undergo a first-order magnetostructural transition (MST) with a large maximum reversible magnetic entropy change of Δ S M  = 16.1 J kg −1  K −1 (this is about a four-fold increase compared to the Δ S M observed for the bulk sample of the same nominal composition) and RC  = 144 J kg −1 for μ o Δ H  = 5 T at temperature T  =  T M  ∼ 245 ± 1 K. The increase in the Δ S M peak value leads to an improved RC compared to that of the bulk sample (122 J kg −1 ). The observed MCE and quasi-reversible character of Δ S M at the MST illustrates the potential of Ni 0.895 Cr 0.105 MnGe 1.05 ribbons for magnetic cooling technology. [ABSTRACT FROM AUTHOR]

• We confirmed that the FM-PM phase transition observed for cubic ErNi 2 Laves compound belongs to second-order magnetic phase transition. • We obtained all of its critical exponent values: β = 0.164(2) and γ = 0.821(9). • The critical behavior of ErNi 2 is close to the Tricritical mean-field model, but there are still differences. In this article, we analyze the critical behavior of the cubic Laves crystalline binary intermetallic compound ErNi 2 near its second-order ferromagnetic (FM) to paramagnetic (PM) transition (6.9 K). Both the normalized thermal dependencies of the magnetic entropy change curves and the Banerjee criterion confirm the second order nature of the transition. By comparing the normalized slopes, we found that the Tricritical mean-field model is the best model to calculate the critical exponent value of ErNi 2. Based on the modified Arrott plots, the final critical exponents are determined to be β = 0.164(2) and γ = 0.821(9), which are the closest to the Tricritical mean-field model, except for a litter differences. Moreover, the accuracy and reliability of these exponents were confirmed by both the Widom scaling relation and the scaling hypothesis. Our results provide new insight into understanding this compound's magnetic interactions. [Display omitted] [ABSTRACT FROM AUTHOR]

The pulsed photoacoustic (PA) technique was used to study the synthesis by laser ablation of silver nanoparticles (Ag-NPs) in ethanol. PA technique allowed to determine the production rate per laser pulse and concentration of synthesized Ag-NPs. The samples were produced by using a pulsed Nd:YAG laser with 1064 nm of wavelength and 7 ns of pulse duration. The laser pulse energy varied from 10 to 100 mJ. Transmission electron microscopy micrographs demonstrated that the obtained nanoparticles were spherical with an average size close to 10 nm. The absorption spectra of the colloids showed a plasmon absorption peak around 400 nm. The PA analyses showed a significant reduction of the production rate of Ag-NPs during the first hundreds of laser pulses. For a higher number of pulses this rate was kept almost constant. Finally, we found that the root mean square (RMS) value of the PA signal was proportional to the laser pulse fluence on the target surface. Thus PA technique was useful to monitor the ablation process. [ABSTRACT FROM AUTHOR]

Highlights: [•] XPS was used to investigate chemical shift in the Nb2SnC and Nb2SC compounds. [•] Valence band of the Nb2SnC and Nb2SC compounds was studied by XPS. [•] Positive and negative chemical shift are observed in the Nb2SnC and Nb2SC. [•] The charge transfer model can be applicable to the Nb2SnC and Nb2SC compounds. [•] The decrease of the N(E F ) of Nb2SC respect to Nb2SnC explain the decrease of T c . [ABSTRACT FROM AUTHOR]

The discharge of an effluent of high salinity from reverse osmosis desalination plants has a strong impact on marine communities. The aim of this study was to examine the effect of brine discharge over soft bottom communities along the Alicante coast (Southeast Spain) over a two year period. Changes in the infaunal assemblage were analysed using univariate and multivariate techniques. Each year we sampled along three transects at three depths (4, 10 and 15m) during winter and summer. We observed a substitution of a community characterized by the presence of Polychaeta, Crustacea and Mollusca, for another dominated by nematodes (up to 98%), in the stations closer to the discharge where salinity values exceed 39 psu. [Copyright &y& Elsevier]