Simple Set-Up for Adiabatic Measurements of Magnetocaloric Effect

Abstract

We present a cost-effective and robust set-up designed to measure directly the magnetic field-induced adiabatic temperature change. The system uses a piston to introduce/remove the sample to/from the magnetic field (μ0∆His up to 1.7T) created by an ordinary electromagnet. The temperature of the sample is controlled by a double pipe heat exchanger operating by the electrical heater and air flow circulation from a Dewar with liquid nitrogen to the sample holder assembly.We have measured the adiabatic temperature change, ΔTad, of two polycrystalline samples: Gd and Ni50Mn35In15Heusler alloy. At the second-order magnetic phase transitions (18oC for Gd and 42oC for Ni50Mn35In15), ΔTadunder μ0∆H=1.7T are 3.8±0.1oC for Gd and 1.9±0.1oC for Ni50Mn35In15. The Heusler alloy shows an inverse magnetocaloric effect: ΔTadis-1.5±0.1oC on cooling and-1.6±0.1oC on heating at the martensitic transformation temperatures of ~24oC and ~29oC, respectively.

Effect of solidification rate on martensitic transformation behavior and adiabatic magnetocaloric effect of Ni50Mn35In15 ribbons

“…The thermal hysteresis is about 13 K for the ribbons, whereas the minimum thermal hysteresis for bulk alloys has been reported to be equal to 4 K [14]. Furthermore, it is worth noting that the martensitic transformations in the ribbons occur at lower temperatures (Table 1) in comparison to the bulk alloy [8,39].…”

“…The Curie temperatures of martensitic (TC M ) and austenitic (TC A ) phases were extracted from M(T) curves by the conventional tangential method [38]. Adiabatic measurements of the magnetocaloric effect were carried out under µ0H = 1.95 T using the set-up described in Ref [39]. In these measurements, to overcome the difficulties with measuring Tad values in a single ribbon, a stack of ribbons with a typical weight of ~20 mg was used, and a thin T-type thermocouple with 0.08 mm in diameter was placed inside the stack.…”

Optimizing the Caloric Properties of Cu-Doped Ni–Mn–Ga Alloys

“…For the selected compositions, magnetization versus temperature curves, M(T), were recorded at 3 K/min under magnetic fields up to 7 T using a vibrating sample magnetometer (VSM; magnetic platform from Cryogenic Ltd. CFMS, London, UK); similarly, strain versus temperature curves, ε(T), under different loads up to 50 MPa were measured using a dynamic mechanical analyzer (DMA Q800, TA Instruments, New Castle, DE, USA) in three-point-bending configuration at 5 K/min. The adiabatic temperature changes associated with the magnetocaloric effect was measured for applied magnetics fields of 1 and 2 T at different temperatures in an own-built set up specially designed for this purpose (see the work of [21] for details). The adiabatic entropy associated with the elastocaloric effect was obtained during compressive loading and unloading up to 100 MPa at a strain rate .…”

“…= 0.01 s −1 . The measurement was performed using a thermocouple attached to a rectangular cuboid-shaped sample at a temperature of T = 310 K. On its turn, Figure 11b shows the temperature dependence of the adiabatic temperature change obtained by direct measurements in a magnetic field up to 1 and 2 T. These measurements were made in an own-built set up specially designed for this purpose (see the work of [21] for details).…”

“…Figure 11a shows the adiabatic temperature changes measured during compressive loading and unloading up to 100 MPa at a strain rate = 0.01 . The measurement was performed using a thermocouple attached to a rectangular cuboid-shaped sample at a temperature of T = 310 K. On its turn, Figure 11b shows the temperature dependence of the adiabatic temperature change obtained by direct measurements in a magnetic field up to 1 and 2 T. These measurements were made in an own-built set up specially designed for this purpose (see the work of [21] for details). It's worth mentioning that, according to Figure 9-and as explained above-application of a 2 T field would promote a maximum transformed fraction of 0.4; similarly, a gross extrapolation to 100 MPa of Figure 10d would yield a maximum entropy between 35% and 40% of the limit value.…”