Direct Measurement of the Magnetocaloric Effect through Time-Dependent Magnetometry

The magnetocaloric effect of a given material is typically assessed through indirect estimates of the isothermal magnetic entropy change, delta S-M. While estimating the adiabatic temperature difference, delta T-ad, is more relevant from the standpoint of refrigeration device engineering, this requires specialized experimental setups. We here present an approach to directly measure delta T(ad )through time-dependent magnetometry in a commercial superconducting quantum interference device (SQUID) device. We use as reference material gadolinium under a 20-kOe field change, and compare our results with those of the literature. Under nonadiabatic experimental conditions, a remarkably similar delta T-ad(T) curve profile is obtained; however, its peak amplitude is underestimated. With a simple compensation methodology we are able to further approximate the profile of the delta T-ad(T) curve obtaining the peak amplitude, the maximizing temperature, and the FWHM within relative errors of -4%, -0.7%, and 11%, respectively. Our reported approach makes the measurement of both delta S-M(T) and delta T-ad(T) possible with a single instrument, enabling accelerated progress towards new, competitive, and industry-ready materials.

Automated summary

This study presents a method to directly measure the parameter ΔT(ad) using a commercial SQUID device. By compensating the measurements, the shape and peak value of the ΔT-ad(T) curve can be approximated, enabling the search for new materials.