Magnetic Field-induced Reverse Transformation Research Articles

ChemInform Abstract: Metamagnetic Shape Memory Effect and Magnetic Properties of Ni‐Mn Based Heusler Alloys

AbstractReview: 46 refs.

Metamagnetic Shape Memory Effect and Magnetic Properties of Ni-Mn Based Heusler Alloys

In some Ni-Mn-In- and Ni-Mn-Sn-based Heusler-type alloys, martensitic transformation from the ferromagnetic parent phase to the paramagnetic martensite phase appears and magnetic field-induced reverse transformation, namely, metamagnetic phase transition, is detected. In this paper, the metamagnetic shape memory effect due to the metamagnetic phase transition and the magnetostress effect in the Ni-Co-Mn-In alloys are introduced and the phase diagrams of Ni50Mn50-yXy (X: In, Sn, Sb) alloys are shown as basic information. Furthermore, the magnetic properties of both the parent and martensite phases in the Ni-Mn-In- and Ni-Mn-Sn-based metamagnetic shape memory alloys are also reviewed.

Kinetic Arrest of Martensitic Transformation in NiCoMnAl Metamagnetic Shape Memory Alloy

Magnetic properties and martensitic transformation behaviors of NiCoMnAl metamagnetic shape memory alloys were investigated. The kinetic arrest phenomenon was observed at about 40 K during thermomagnetization measurements. At temperatures ranging from 4.2 to 200 K, magnetic field-induced reverse transformation was confirmed by a pulse magnetometer with a magnetic field up to 45 T. By plotting the equilibrium magnetic fields against the measured temperature, the transformation entropy change was calculated by using the Clausius-Clapeyron equation. The transformation entropy change was found to become zero below 40 K, which can explain the appearance of the kinetic arrest phenomenon.

Magnetic field-induced reverse transformation in B2-type NiCoMnAl shape memory alloys

Effects of the addition of Co to the NiMnAl alloy on the martensitic and magnetic properties were investigated. The magnetic properties of the parent (P) phase drastically changed from paramagnetic to ferromagnetic, while the magnetization in the martensite (M) phase slightly decreased with increasing Co composition. Consequently, in the Ni40Co10Mn33Al17 alloy with the B2 ordered structure, the martensitic transformation from a ferromagnetic P to a weak magnetic M phase was obtained. The martensitic transformation temperatures in this alloy decreased by about 30K with the application of a magnetic field of 7T and a metamagnetic phase transformation was confirmed.