Temperature–Frequency Dependence of the Magnetocaloric Effect Near the T C in the Ni 50 Mn 28 Ga 22 Alloy in Cyclic Magnetic Fields

The results of studying the influence of the frequency (up to 20 Hz) of a cyclic magnetic field of 0.62 and 1.2 T on the value of the adiabatic temperature change in the Ni 50 Mn 28 Ga 22 alloy are presented. In a cyclic magnetic field of 0.62 T at a frequency of f = 1 Hz, the maximum value of Δ T ad = 0.44 K. With an increase in the frequency of the cyclic field, a monotonic decrease in the value of ∆ T ad is observed, for f = 20 Hz, Δ T ad = 0.28 K, i.e., the effect decreases by 36%, while in a field of 1.2 T, the decrease in the effect with an increase in the frequency of the cyclic magnetic field is approximately 41%. A decrease in the relative cooling power with increasing frequency of the cyclic magnetic field from 19.5 K 2 at f = 1 Hz to 10.4 K 2 for f = 20 Hz (in a field of 1.2 T) was found. The observed frequency dependence of the MCE near T C is a consequence of the inhomogeneous microstructure of the sample. Long-term exposure to a cyclic magnetic field of 1.2 T at different frequencies (2, 5, 10, and 15 Hz) shows the stability of the effect without signs of degradation.