Influence of the demagnetizing field on the determination of the magnetocaloric effect from magnetization curves

The influence of the demagnetizing factor (N) on the magnetic entropy change (DSM) curves is studied for materials with a second order phase transition. For this purpose, a soft magnetic amorphous ribbon is measured for different orientations of the magnetic field with respect to the plane of the sample. For temperatures below the Curie temperature (TC), the increase in N causes a decrease in DSM, while for temperatures above TC no change in the shape of the curves has been found for the different orientations, as expected. In order to eliminate this influence of N and compare the DSM(T) curves for samples with different shapes, the recently proposed universal curve for the magnetocaloric effect can be used

Influence of Co and Ni addition on the magnetocaloric effect in Fe88−2xCoxNixZr7B4Cu1 soft magnetic amorphous alloys

We have studied the magnetocaloric effect in a series of Fe88−2xCoxNixZr7B4Cu1Fe88−2xCoxNixZr7B4Cu1alloys. The partial substitution of Fe by Co and Ni leads to a monotonic increase in the Curie temperature(TC)(TC) of the alloys from 287 K for x=0x=0 to 626 K for x=11x=11. The maximum magnetic entropy change (ΔSpkM)(ΔSMpk) at an applied field of 1.5 T, shows a value of 1.98 J K−1 kg−11.98 J K−1 kg−1 for x=8.25x=8.25. The refrigerant capacity (RC) has maximum values near 166 J kg−1166 J kg−1 (for x=0x=0 and 2.75). These values place the present series of alloys among the best magnetic refrigerant materials, with an RC ∼40%∼40% larger than Gd5Si2Ge1.9Fe0.1Gd5Si2Ge1.9Fe0.1 and ∼15%∼15% larger than Fe-based amorphousalloys

Magnetocaloric effect and critical exponents of Fe77Co 5.5Ni5.5Zr7B4Cu1: A detailed study

The critical exponents of the alloy have been determined with the Kouvel–Fisher method to predict the field dependence of the magnetic entropy change DSM . The nonlinear fit of DSM ðHÞ to a power law provides a field exponent in perfect agreement with the predictions of the relevant scaling laws using the obtained critical exponent values. It is shown that possible discrepancies between these two methods for determining the field dependence of DSM might arise due to a poor resolution in the temperature of the experiments

Optimization of the refrigerant capacity in multiphase magnetocaloric materials

The refrigerant capacity (RC) of magnetocaloric materials can be enhanced using multiphase materials or composites, which expand the temperature range over which a significant magnetic entropy change can be obtained. Numerical simulations show that by controlling the parameters of the composite (the fraction of the different phases and their Curie temperatures) improvements of RC of ∼83% are possible. The maximum applied field plays a crucial, nonmonotonic, role in the optimization. As a proof of concept, it is shown that the combination of two Fe88−2xCoxNixZr7B4Cu1 alloys produces an enhancement in RC of ∼37%, making it ∼92% larger than that of Gd5Si2Ge1.9Fe0.

Capacitated vehicle routing problem model for carriers

Background: The Capacitated Vehicle Routing Problem (CVRP) is one of the most important transportation problems in logistics and supply chain management. The standard CVRP considers a fleet of vehicles with homogeneous capacity that depart from a warehouse, collect products from (or deliver products to) a set of customer locations (points) and return to the same warehouse. However, the operation of carrier companies and third-party transportation providers may follow a different network flow for collection and delivery. This may lead to non-optimal route planning through the use of the standard CVRP. Objective: To propose a model for carrier companies to obtain optimal route planning. Method: A Capacitated Vehicle Routing Problem for Carriers (CVRPfC) model is used to consider the distribution scenario where a fleet of vehicles depart from a vehicle storage depot, collect products from a set of customer points and deliver them to a specific warehouse before returning to the vehicle storage depot. Validation of the model’s functionality was performed with adapted CVRP test problems from the Vehicle Routing Problem LIBrary. Following this, an assessment of the model’s economic impact was performed and validated with data from a real carrier (real instance) with the previously described distribution scenario. Results: The route planning obtained through the CVRPfC model accurately described the network flow of the real instance and significantly reduced its distribution costs. Conclusion: The CVRPfC model can thus improve the competitiveness of the carriers by providing better fares to their customers, reducing their distribution costs in the process

Mechanically induced disorder and crystallization process in Ni-Mn-In ball-milled alloys

[EN] High mechanical deformation has been induced in a Ni-Mn-In metamagnetic shape memory alloy by means of ball milling. The evolution of both the martensitic transformation and the magnetic properties associated to the microstructural variations has been characterized. The as-milled nanometric particles display an amorphous structure with a frustrated magnetic state compatible with a canonical spin-glass. On heating, an abrupt crystallization process occurs around 500 K leading to a cubic B2 structure, which, in turn, does not show martensitic transformation. Modified Arrott plots point to competing long- and short-range magnetic couplings in the B2 structure. On further heating, a relaxation process takes place above 700 K concurrently with a B2-L21 atomic ordering, giving rise to an anomalous two-step thermal expansion. The combined effect of both processes makes possible the subsequent occurrence of a martensitic transformation, which takes place at the same temperature than in the bulk. The large relative-cooling-power linked to the magnetocaloric effect at the martensitic transformation in the annealed powder makes it interesting for practical applications of magnetic refrigeration at nanoscale.This work has been carried out with the financial support of the Spanish “Ministerio de Economía y Competitividad” (Projects number MAT2012-37923-C02 and MAT2015-65165-C2-R). We also acknowledge ILL and SpINS for beam time allocation (experiment CRG-2158). RCF acknowledges a Postdoctoral fellowship from the Univeridad Pública de Navarra (grant number: 1081/2015). JARV acknowledges CSIC for a JAEdoc contract. J. Pons is acknowledged for TEM observations