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The structure and the magnetic transitions have been investigated as a function of Mn in stoichiometric Ni2MnGa heusler alloys. Particular attention is paid to examine the linear increase of martensite transformation temperature on substituting Mn for Ga. It is observed that the martensite temperature increases and Curie temperature decreases with the effect of Mn content. Room-temperature magnetic measurements show the composition-dependent characteristics with decreasing magnetic saturation values and increasing coercivity values due to decrease in the magnetic exchange interaction strength with increasing Mn in place of Ga. The scanning electron microscopy image confirms that the Mn-rich alloys have the martensitic plates. [ABSTRACT FROM AUTHOR]

Ferromagnetic shape memory alloy (FSMA) is one of the smart materials which finds increasing industrial applications. This paper deals with the effect of Mn substitution for Ga on martensitic and magnetic transformation temperature of polycrystalline Ni-Mn-Ga alloy prepared in argon atmosphere. The prepared alloy has been characterized by means of scanning electron microscopy (SEM), differential scanning calorimeter (DSC), and superconducting quantum interference device (SQUID). Magnetic property of alloy has been analyzed with vibrating sample magnetometer (VSM). From the VSM measurement, it is studied that the saturation magnetization of polycrystalline ferromagnetic shape memory occurs at high magnetic field. The main finding of this article is the raise in transformation temperature by 28 K/atom. As the working temperature is above room temperature, it seems to be a promising candidate for practical applications. The result reported here may help for further research in the field of polycrystalline Ni-Mn-Ga alloy. [ABSTRACT FROM AUTHOR]

Abstract: Aim of this paper is to study the transformation temperature of Ni–Mn–Ga single crystals by using differential scanning calorimetry. It shows that martensitic temperature abruptly increase with increasing Mn concentration whereas Curie transition to decrease. The calculated value of electron-to-atom ratio (e/a) reveal that it increases with increased doping of Mn in place of Ga at fixed Ni content. The crystal structures at room temperature were studied using XRD pattern. Thermo-magnetic behavior of the Ni–Mn–Ga alloy shows the ferromagnetic nature and its behaviour is slightly losing due to antiferromagnetic ordering of excess Mn atoms. Microstructure from SEM image confirm that the alloys are martensitic plates. The martensitic plates contain fewer stripes like magnetic domains. [Copyright &y& Elsevier]