Direct magnetocaloric characterization and simulation of thermomagnetic cycles

Abstract

An experimental setup for the direct measurement of the magnetocaloric effect capable of simulating high frequency magnetothermal cycles on laboratory-scale samples is described. The study of the magnetocaloric properties of working materials under operative conditions is fundamental for the development of innovative devices. Frequency and time dependent characterization can provide essential information on intrinsic features such as magnetic field induced fatigue in materials undergoing first order magnetic phase transitions. A full characterization of the adiabatic temperature change performed for a sample of Gadolinium across its Curie transition shows the good agreement between our results and literature data and in-field differential scanning calorimetry. © 2013 AIP Publishing LLC. [http://dx

Influence of thermal conductivity on the dynamic response of magnetocaloric materials

“…The adiabatic temperature change measured for the gadolinium sample (k Gd = 10 Wm −1 K −1 ) was ∆T ad = 2.10 ±0.15 K, in agreement with previous work (Porcari et al, 2013): the time constant of its adiabatic branches corresponded to τ = 0.11 s. We measured ∆T ad = 2.10 ± 0.15 K for the parent MnFePSi for a magnetic field change of 1 T, which is reasonable given recent reports on Fe 2 P-based systems . The thermal hysteresis of this material, measured from magnetization isofields at a sweep rate of 1 Kmin −1 , is 1.8 K; its thermal conductivity across the first-order transition was determined to be k MnFePSi = 3.5 Wm −1 K −1 and the time constant associated with the temperature change τ = 0.12 s. A second composite material was also prepared to test a Fe 2 P-based system with a lower thermal conductivity than its parent alloy: a mixture of MnFePSi and epoxy (20 wt.% and k MnFePSi+epoxy = 1.25 Wm…”

“…1 a) between two regions with controlled temperature and magnetic field (Porcari et al, 2013). The temperature sensor used was a Lakeshore Cernox TM thermoresistor (bare chip) (2) .…”

Field-temperature phase diagrams of freestanding and substrate-constrained epitaxial Ni-Mn-Ga-Co films for magnetocaloric applications

“…As magnetization, strain, and volume commonly change at a ferroic transition, it can be induced not only by temperature but also magnetic fields, mechanical stress, hydrostatic pressure, or even a combination of those. 2 Usually, the associated magnetocaloric, elastocaloric, or barocaloric effects are maximal in materials with first-order phase transitions, 3 but their cyclic performance is still a challenge due to irreversible effects, 4,5 fatigue, 6 and, of course, hysteresis. It was proposed to use minor loops 7 or artificial phase nucleation sites, 8 but still a more detailed understanding of thermal and magnetic hysteresis is required in order to decrease hysteresis.…”

Interfacial Thermal Resistance in Magnetocaloric Epoxy‐Bonded La‐Fe‐Co‐Si Composites

“…A detailed description of the setup can be found in Ref. . In the reported experiments, two parts of the same sample were overlapping to increase its thermal mass.…”