I.S. Titov

Magnetic, transport, and magnetocaloric properties of boron doped Ni-Mn-In alloys

The impact of B substitution in Ni50Mn35In15−xBx Heusler alloys on the structural, magnetic, transport, and parameters of the magnetocaloric effect (MCE) has been studied by means of room-temperature X-ray diffraction and thermomagnetic measurements (in magnetic fields (H) up to 5 T, and in the temperature interval 5–400 K). Direct adiabatic temperature change (ΔTAD) measurements have been carried out for an applied magnetic field change of 1.8 T. The transition temperatures (T-x) phase diagram has been constructed for H = 0.005 T. The MCE parameters were found to be comparable to those observed in other MCE materials such as Ni50Mn34.8In14.2B and Ni50Mn35In14X (X=In, Al, and Ge) Heusler alloys. The maximum absolute value of ΔTAD = 2.5 K was observed at the magnetostructural transition for Ni50Mn35In14.5B0.5.

Quasi-Diamagnetism and Exchange Anisotropy in Ni–Mn–In–Co Heusler Alloys

The quasi-diamagnetism effect that manifests itself in the negative magnetic susceptibility observed in weak magnetic fields during cooling of samples below some critical temperature has been revealed in Ni48Co2Mn35In15 Heusler alloys. The effect has been attributed to a strong nonequilibrium of the system due to the presence of magnetic and structural disorders and exchange anisotropy.

Magneto-Optical Study of Martensitic Transition in Ni45Mn36.7In13.3Co5 (at. %) Single Crystals

Transverse Kerr effect (TKE) was used to study magneto-optical (MO) properties of Ni45Mn36.7In13.3Co5 (at.%) single crystals. A single crystalline ingot of such composition was grown by the Czochralski method. One series of samples was quenched into cold water (WQ) and the other series after quenching was heated at 770 K for 20 min and slowly cooled to assure a complete atomic order (SC). Accordingly to differential scanning calorimetry (DSC), magnetic and magneto-optical (MO) measurements, WQ samples exhibit well-defined martensitic transition (MT), but the SC samples do not show MT. It is found that TKE for WQ samples shows the following features (i) MO signal is well pronounced far below the martensitic transition in spite of a weak magnetization of martensitic phase; (ii) the characteristic temperatures of martensitic transition differ from those for the bulk and depend on annealing conditions; (iii) MO spectra profile do not change significantly during the martensitic transition and is similar but not identical with that for Ni50Mn35In15 thin films and Ni43.7Mn43.6In12.7 ribbons measured before; (iv) MO signal is anisotropic.