Magnetic superelasticity and inverse magnetocaloric effect in Ni-Mn-In

Applying a magnetic field to a ferromagnetic ${\mathrm{Ni}}_{50}{\mathrm{Mn}}_{34}{\mathrm{In}}_{16}$ alloy in the martensitic state induces a structural phase transition to the austenitic state. This is accompanied by a strain which recovers on removing the magnetic field, giving the system a magnetically superelastic character. A further property of this alloy is that it also shows the inverse magnetocaloric effect. The magnetic superelasticity and the inverse magnetocaloric effect in Ni-Mn-In and their association with the first-order structural transition are studied by magnetization, strain, and neutron-diffraction studies under magnetic field.

Figure 1

(Color online) Features in the martensitic transformation associated with temperature and magnetic-field dependence. (a) Calorimetric curves across the martensitic transition. The horizontal arrows indicate the direction of temperature change. (b) Magnetization as a function of magnetic field measured on increasing field in the vicinity of the martensitic transition. The red (dark gray) lines drawn through the data points (shown only for the $200\mathrm{K}$ data) cross at a point corresponding to the characteristic field around which the metamagnetic transition begins to occur.

Figure 2

The relative length change in constant applied magnetic fields of 0, 2, and $5\mathrm{T}$. The arrows indicate the positions of $M_s$.

Figure 3

Characteristic field-dependent properties around the martensitic transition. (a) Shift in the martensitic transition temperature as a function of magnetic field for ${\mathrm{Ni}}_{50.3}{\mathrm{Mn}}_{33.8}{\mathrm{In}}_{15.9}$, ${\mathrm{Ni}}_2\mathrm{Mn}\mathrm{Ga}$, and ${\mathrm{Ni}}_{53.5}{\mathrm{Mn}}_{19.5}{\mathrm{Ga}}_{27}$. (b) Temperature dependence of the magnetization obtained at selected fields from Fig. 1b. The numbers refer to magnetic field values in Tesla. (c) The difference between the magnetizations in the cubic and martensite phases. $\Delta M$ saturates at about $0.5\mathrm{T}$. The lines drawn through the data are guides.

Figure 4

(Color online) The magnetic-field dependence of the magnetization for the sample used in the neutron-diffraction experiments. The crossing point of the red (dark gray) lines determines $H_c$. The data with open symbols correspond to the isotherm at which the neutron-diffraction experiments were made.

Figure 5

(Color online) Neutron diffractograms. (a) Patterns at $317\mathrm{K}$ $\left(L{2}_1\right)$ and $5\mathrm{K}$ ($10\mathrm{M}$ martensite). (b) The field dependence of the diffraction pattern at $180\mathrm{K}$ showing the field-induced transformation from the martensite to the austenite state.

Figure 6

Magnetic-field dependence of strain at $195\mathrm{K}$ $(T<M_s)$ and $295\mathrm{K}$ $\left(L{2}_1\right)$. The strain recovers on removing the field indicating magnetically superelastic behavior. Arrows show the direction of field change.

Figure 7

The magnetic-field dependence of the magnetization at $195\mathrm{K}$.

Figure 8

Temperature dependence of $\Delta S$.