Magnetocaloric Effect of Gadolinium at Adiabatic and Quasi-Isothermal Conditions in High Magnetic Fields

TL;DR

This study introduces a new calorimetric method to measure the magnetocaloric effect of gadolinium under adiabatic and quasi-isothermal conditions in high magnetic fields, providing direct heat transfer data relevant for magnetic refrigeration.

Contribution

A novel experimental setup was developed for simultaneous measurement of MCE at adiabatic and quasi-isothermal conditions in high magnetic fields.

Findings

Maximum deltaT of 17.7 K at 140 kOe

Maximum deltaQ of 5900 J/kg at 20°C and 140 kOe

Effective measurement of heat transfer in magnetocaloric materials

Abstract

High cooling power of magnetocaloric refrigeration can be achieved only at large amounts of heat, which can be transferred in one cycle from cold end to hot end at quasi-isothermal conditions. The simple experimental method for direct measurement of the transferred heat from material with magnetocaloric effect (MCE) to massive nonmagnetic block at quasi-isothermal conditions was proposed. The vacuum calorimeter was designed for the simultaneous measurements of MCE both at adiabatic conditions (deltaT) and quasi-isothermal conditions (deltaQ) in the magnetic fields of Bitter coil magnet. This calorimeter was tested on samples of pure polycrystalline Gd with direct MCE. The maximal obtained values were deltaT = 17.7 K and deltaQ = 5900 J/kg at initial temperature 20 0C in magnetic field 140 kOe.