Ni-Mn-In-Co

In Ni–Mn–In–Co alloys, a magnetic field induced phase transformation occurs, where the martensite with a very low magnetization transforms into a ferromagnetic austenite upon application of a magnetic field. We investigated the magnetic field dependence of martensitic transformation behavior in a series of Ni_50-xMn₃₇In₁₃Co_x (x=0-9). An optimized composition range of 4.5≤x≤5.5 is obtained where the magnetic field induced martensitic transformation is realized. 

Reversibility of the magnetostructural transition is of crucial importance for magnetic actuator materials. It is desirable that the austenite induced by the magnetic field is able to transform back to the initial martensite when the magnetic field is removed. A complete recovery of the initial martensite state may bring about magneto-elasticity, while the irreversible magnetostructural transition would result in magneto-plasticity. By analyzing isothermal magnetization curves under magnetic field cycling, the reversibility of the magnetostructural transition was investigated in Ni₄₅Mn₃₇In₁₃Co₅ in form of bulk sample and melt-spun ribbons. Hysteresis in the thermally and magnetically induced martensitic transformation plays an important role in the reversibility of the magnetostructural transition. In ribbons with a large hysteresis of 18 K, a residual field-induced austenite is present after removing the magnetic field, while, in the bulk sample, the magnetostructural transition is reversible at moderate temperatures due to a relatively small hysteresis of 8 K.