Temperature-Frequency Dependence of the Magnetocaloric Effect Near the TC in the Ni50Mn28Ga22 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 Ni50Mn28Ga22 alloy are presented. In a cyclic magnetic field of 0.62 T at a frequency of f = 1 Hz, the maximum value of Delta T-ad = 0.44 K. With an increase in the frequency of the cyclic field, a monotonic decrease in the value of increment T-ad is observed, for f = 20 Hz, Delta 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.