Abstract
Results of investigation of the temperature dependence of magnetization of Ni2.08Mn0.96Ga0.96 alloy in the magnetic fields of various intensities are reported. An abrupt change in magnetization at transformation of low temperature phase to the high temperature one is observed. Magnetization increases during the phase transition in the magnetic field having intensity below 500 kA/m and decreases at higher intensities. The explanation is based on zigzag configuration of domains in twinned structure. In the Curie temperature region the ferromagnetic ? paramagnetic phase transition occurs sharply at low field strength, while at higher field strength the transition is smooth. It is concluded that the increase in flatness of the curve σ = f (T) and the increase of ferromagnetic state destruction temperature with increase of the intensity of the magnetic field is indicative of the main role of Mn in magnetization of the alloy.
Highlights
Owing to the fact that martensitic phase transition occurs in Ni-Mn-Ga alloys in room temperature region, they exhibit shape memory effect (SME) [1]
The essential influence of magnetic field with intensity below 916 kA/m on twin plate dimensions and theirs distribution in low temperature phase formed during martensitic transformation without applying of magnetic field has not been revealed
From curve 1 in Figure 2 (H = 24 kA/m) it is seen that magnetization of low temperature phase remains equal to σ/σs, arb, unit
Summary
Owing to the fact that martensitic phase transition occurs in Ni-Mn-Ga alloys in room temperature region, they exhibit shape memory effect (SME) [1]. It is known that phases forming in Ni-Mn-Ga system alloys before and after martensitic transformation are ferromagnetic [2] Such feature of these materials allows controlling the effect of shape memory by means of the external magnetic field [3]. Measurement made in the magnetic field of low intensity has revealed an abrupt increase in magnetization on the temperature dependence of magnetization for Ni2MnGa alloy This increase is attributed to the change in magnetocrystalline anisotropy constant at phase transformation [5,6,7]. In order to obtain additional data on the change of alloys physical properties during the phase transitions we carry out the investigation of temperature dependence of magnetization of polycrystalline Ni2.08Mn0.96 Ga0.96 alloy in magnetic fields of various intensities.
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