Simple practical system for directly measuring magnetocaloric effects under large magnetic fields

Area of Science:

• Materials Science
• Condensed Matter Physics
• Magnetism

Background:

• The magnetocaloric effect (MCE) is crucial for magnetic refrigeration technologies.
• Accurate measurement of adiabatic temperature change (ΔT_ad) is essential for evaluating MCE materials.
• Existing methods may have limitations in measuring ΔT_ad under various conditions.

Purpose of the Study:

• To directly measure the adiabatic temperature change (ΔT_ad) in Gadolinium (Gd) and Mn_1.15Fe_0.8P_0.5Si_0.5C_0.05.
• To investigate the magnetic field dependence of ΔT_ad for these materials.
• To demonstrate the capability of a homemade adiabatic magnetocalorimeter for broad material characterization.

Main Methods:

• Utilized a homemade adiabatic magnetocalorimeter operating between 260-360 K and 0-7 T.
• Employed a servo motor for sample manipulation within a vacuum environment provided by the Physical Property Measurement System (PPMS).
• Directly measured ΔT_ad for Gd and Mn_1.15Fe_0.8P_0.5Si_0.5C_0.05 samples.

Main Results:

• Peak ΔT_ad values of 8.71 K (Gd) and 6.41 K (MnFePSiC) were recorded at 7 T.
• Gd exhibited ΔT_ad ∝ H^2/3 dependence, characteristic of second-order magnetic transitions.
• MnFePSiC showed ΔT_ad ∝ H^0.66-1.04 dependence, indicative of first-order magnetic transitions.

Conclusions:

• The developed magnetocalorimeter accurately measures ΔT_ad across a range of magnetic fields and temperatures.
• The study provides insights into the magnetic transition behavior of Gd and MnFePSiC.
• The instrument is versatile for characterizing various magnetic materials for MCE applications.