Consequenses of the magnetocaloric effect on magnetometry measurements

Magnetization curves recorded at high sweep-rates on magnetic materials near a phase transition temperature can be affected by temperature changes in the material due to the magnetocaloric effect. This change in the sample temperature is a result of the quasiadiabatic conditions that can occur under such conditions and we demonstrate its effects on magnetization curves of two magnetocaloric materials, La(Fe0.945Co0.055)11.9Si1.1 and Gd5Si2Ge2. We show how a quantity calculated from isothermal magnetization curves, the magnetic entropy change, ΔSM, is affected by the erroneous data. As ΔSM is a measure of the magnetocaloric effect, the discrepancies demonstrated here are more severe close to a peak in ΔSM, which is precisely the quantity that is of interest and reported on in the literature from possibly erroneous magnetization data. We also demonstrate how, through simple measurements and without a direct measurement of the sample temperature, one can determine an appropriate sweep-rate of the magnetic field.