Adiabatic Temperature Changes at Structural and Magnetic Phase Transitions in Ni45Mn43CoSn11 at High Magnetic Fields

The adiabatic temperature change (Δ Tad) in Ni45Mn43CoSn11 has been measured by a direct method in magnetic field changes up to 14 T. Large reversible magnetocaloric effects resulting in Δ Tad of about =-11 and 5 K have been observed for magnetic field changes of 14 T at the magnetostructural (TA ∼ 260 K) and magnetic transitions (TC ∼ 320 K), respectively. The impact of the thermomagnetic history on Δ Tad at high magnetic fields has been reported. The significant observed changes in the relaxation time of Δ Tad, depending on the type of the phase transitions, magnetization, and demagnetization cycle are discussed

Relaxation phenomena in adiabatic temperature changes near magnetostructural transitions in Heusler alloys

The relaxation processes of the adiabatic temperature changes (ΔTad) at the phase transitions in Ni45Mn43CoSn11, Ni50Mn36.5In13.5, and Ni50Mn35In14.25B0.75 Heusler alloys with different magnetic structures have been studied using a direct extraction method in magnetic fields up to 14 T. It has been found that ΔTad exhibits short relaxation times (less than 10−1 (s)) in the vicinity of the second order phase transitions at the Curie temperatures. The relaxation times of the first order martensitic transitions strongly depend on the latent heat of the transition and can be characterized by a logarithmic law

Kinetic effects in the magnetic and magnetocaloric properties of metamagnetic Ni50Mn35In14.25B0.75

Ni50Mn35In14.25B0.75 is a typical representative of the family of metamagnetic In-based Heusler alloys which shows large magnetocaloric effects generated from first order magnetostructural and ferromagnetic-paramagnetic transitions. For this alloy, a study of the adiabatic temperature change ΔTad by a direct method and through thermomagnetic measurements in magnetic fields up to 14 T has been performed. It has been shown that the rate of heating/cooling can affect the magnitude and sign of ΔTad. The application of magnetic fields larger than 12 T (on cooling) results in the “kinetic arrest” of the ferromagnetic austenitic phase. The effects of the temperature and magnetic history, and kinetic effects, on ΔTad of these Ni-Mn-In-based Heusler alloys in high magnetic fields are discussed