Deciphering M-T diagram of shape memory Heusler alloys: reentrance, plateau and beyond

We present our recent results on temperature behaviour of magnetization observed in Ni_47Mn_39In_14 Heusler alloys. Three regions can be distinguished in the M-T diagram: (I) low temperature martensitic phase (with the Curie temperature T_CM = 140 K), (II) intermediate mixed phase (with the critical temperature T_MS = 230 K) exhibiting a reentrant like behavior (between T_CM and T_MS) and (III) high temperature austenitic phase (with the Curie temperature T_CA = 320 K) exhibiting a rather wide plateau region (between T_MS and T_CA). By arguing that powerful structural transformations, causing drastic modifications of the domain structure in alloys, would also trigger strong fluctuations of the order parameters throughout the entire M-T diagram, we were able to successfully fit all the data by incorporating Gaussian fluctuations (both above and below the above three critical temperatures) into the Ginzburg-Landau scenario

Research of magnetocaloric effect of Ni-Mn-In-Co- based Heusler alloys by the direct method in magnetic fields up to 14 T

IEEE International Magnetics Conference, INTERMAG 2017 ( 2017. Dublin; Ireland

Direct and inverse magnetocaloric effect in ni1.81mn1.64in0.55 multifunctional heusler alloy

Moscow International Symposium on Magnetism, MISM 2014 (6. 2014. Moscow; Russian Federation

Non-Collinear Phase in Rare-Earth Iron Garnet Films near the Compensation Temperature

The experimental discovery of the suppression effect of the non-collinear phase in strong magnetic fields near the compensation point in ferrimagnetic structures was made. The observations were carried out using the magneto-optical method by creating a lateral temperature gradient in the plane of the epitaxial films of iron garnets. The non-collinear phase is absent in weak magnetic fields. If an external magnetic field exceeds the first critical value, the non-collinear phase arises near the compensation point. The temperature range of the non-collinear phase expands due to the field increase up to the second critical value. Further field increases conversely reduce the temperature range of the non-collinear phase so that the field above the second critical value causes the disappearance of the non-collinear phase. The effect of the occurrence and suppression of the non-collinear phase is demonstrated on samples of two types of iron garnet films with two and three magnetic sublattices. Phase diagrams of the magnetic states in the vicinity of the critical point are constructed, and it is shown that the region of existence of the non-collinear phase in a two-sublattice magnet is smaller than in a three-sublattice one

Magnetocaloric Effect, Structure, Spinodal Decomposition and Phase Transformations Heusler Alloy Ni-Mn-In

Ni46Mn41In13 (close to 2-1-1 system) Heusler alloy was studied by magnetization measurement dependence on the temperature in magnetic fields of up to 13.5 T. The magnetocaloric effect measured by the direct method in quasi-adiabatic conditions showed a maximum value of ∆Tad = −4.2 K at a temperature T = 212 K in a magnetic field of 10 T in the region of martensitic transformation. The structure of the alloy was studied by transmission electron microscopy (TEM) as a function of the temperature and the thickness of the sample foil. In the temperature range from 353 to 215 K, at least two processes were established. The results of the study indicate that the concentration stratification occurs according to the mechanism of spinodal decomposition (conditionally spinodal decomposition) into nanoscale regions. At a temperature of 215 K and lower, martensitic phase with 14 M modulation is observed in the alloy at thicknesses greater than 50 nm. Some austenite is also observed. In foils with thickness of less than 50 nm in a temperature range from 353 to 100 Km only the initial austenite, which has not transformed, was found