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Phase Transitions in the Ni2.14Mn0.81Fe0.05Ga Heusler Alloy under the Influence of a Magnetic Fild and Hydrostatic Pressure
Heusler alloys of the Ni2MnX family, where X = Ga, In, Sn, …, which have been shown to exhibit
giant magnetocaloric effect (MCE) and magnetically controlled shape memory effect due to thermoelastic
magnetostructural phase transition (MSPT), continue to attract attention. However, these functional prop-
erties are fully manifested in strong magnetic fields of at least several T. Currently, there is an active search for
alloys in which these effects could manifest themselves in fields that do not exceed those created by perma-
nent magnets. Accurate measurement and theoretical calculation of the effect of multicomponent alloying on
the bulk magnetostrictive constant B may serve as a guideline for the development of new multifunctional
Heusler alloys. Thermodynamic theory shows that B can determine both the sensitivity of the MSPT to the
external field and the sign of the MCE. In this paper, the effects of magnetic field and external hydrostatic
pressure on the MSPT in Ni2.14Mn 0.81Fe0.05Ga Heusler alloy with direct MCE are investigated. It was found
that a magnetic field contributes to an increase in the temperature of the MSPT, while hydrostatic compres-
sion contributes to an increase in magnetization at the Curie point, slightly affecting its position. The ther-
modynamic model based on the Landau expansion correctly describes the experimental data taking into
account the bulk magnetostrictive constant B.