Magnetocaloric effect in some magnetic materials in alternating magnetic fields up to 22 Hz

TL;DR

This study measures the magnetocaloric effect in various magnetic materials under alternating magnetic fields up to 22 Hz, revealing how frequency influences MCE and implications for magnetic refrigeration efficiency.

Contribution

It provides the first detailed analysis of MCE behavior in different materials under low-frequency alternating fields, highlighting frequency effects on magnetocaloric performance.

Findings

Gd shows minimal MCE change with frequency.

Ni2.07Co0.09Mn0.84Ga MCE vanishes near 20 Hz.

Frequency increase can enhance magnetic refrigerator efficiency.

Abstract

Direct measurements of the magnetocaloric effect (MCE) in different materials (Gd, Fe48Rh52, Ni43Mn37.9In12.1Co7 and Ni2.07Co0.09Mn0.84Ga) in alternating magnetic fields with frequencies f < 22 Hz and an amplitude deltaH = 6.2 kOe are carried out. The MCE in Gd shows inconsiderable changes with field frequency. Near paramagnetic-ferromagnetic phase transition in Ni43Mn37.9In12.1Co7 Heusler alloy a slight reduction of MCE with frequency is observed. In weak alternating fields in materials with AFM-FM magneto-structural phase transitions (Fe48Rh52, Ni43Mn37.9In12.1Co7) it is not possible to get a structural contribution to overall MCE because of irreversibility of the transitions in these fields. Near magneto-structural phase transitions the MCE in these alloys has only magnetic contribution, and does not show a significant dependence on the magnetic field frequency. In Ni2.07Co0.09Mn0.84Ga Heusler alloy the MCE vanishes at frequencies about 20 Hz. The obtained results show the increase of frequencies of operating cycles is one of the powerful methods to improve the efficiency of magnetic refrigerators in case of Gd as a refrigerant.