Direct observation of magnetocaloric effect by differential thermal analysis: influence of experimental parameters

TL;DR

This study introduces an experimental setup using differential thermal analysis to observe the magnetocaloric effect in magnetic materials, examining how experimental parameters like magnetic field ramp rate influence the effect.

Contribution

The paper presents a novel differential thermal analysis method to measure the magnetocaloric effect and analyzes the influence of magnetic field ramp rate on the effect's intensity.

Findings

Magnetocaloric effect increases with magnetic field change rate.

Effective heat capacity of the system was determined using calorimetric measurements.

The method allows for accurate subtraction of environmental effects to measure adiabatic temperature change.

Abstract

The magnetocaloric effect is the isothermal change of magnetic entropy and the adiabatic temperature change induced in a magnetic material when an external magnetic field is applied. In this work, we present an experimental setup to study this effect in metamagnetic transitions, using the differential thermal analysis technique, which consists in measuring simultaneously the temperatures of the sample of interest and a reference one while an external magnetic field ramp is applied. We have tested our system to measure the magnetocaloric effect in La0.305Pr0.32Ca0.375MnO3, which presents phase separation effects at low temperatures (T < 200 K). We obtain \DeltaT vs H curves, and analyze how the effect varies by changing the rate of the magnetic field ramp. Our results show that the intensity of the effect increases with the magnetic field change rate. We also have obtained the effective heat capacity of the system without the sample by performing calorimetric measurements using a pulse heat method, fitting the temperature change with a two tau description. With this analysis, we are able to describe the influence of the environment and subtract it to calculate the adiabatic temperature change of the sample.