Heusler alloys of Ni₂MnGa, and its off-stoichimetry or substituted derivatives, show multiferroic properties including the magnetic shape memory effect (MSM) [1-2]. This property has received significant attention due to its application potential in micropumps, actuators, and sensors [3]. The magneto-crystalline anisotropy of the martensite states is a key requirement allowing magnetic-field induced reorientation (MIR) of twin domains that defines the magnetic shape memory effect.

Magnetotransport properties of Ni₂MnGa has gained far less attention than its magnetoelastic investigation. Difficulties in maintaining a single variant state, as well as complications in maintain electrical contacts during the up to 12 % magnetic field induced strains has hindered electrical transport investigations. Results will be present of extensive magnetotransport measurements (resistivity and magnetoresistance) of single crystalline Ni₅₀Mn₂₅Ga₂₀Fe₅. The material undergoes martensitic transformation into the 10M MIR-active phase on cooling below T_mart = 309 K, as well as further inter-martensitic transformations into the 14M and non-modulated (NM) phases on further cooling.

To maintain a single-variant state in 10M martensite, a custom-built in-situ compression device was used. Despite maintaining a unique short axis, the inter-martensitic transformations to 14M and NM phases inevitably result in multi-variant states. Both the device, and the results of the anisotropic magnetotransport measurements across these phase transitions in this intriguing multiferroic material will be present.

References:

[1] A. Brzoza, S. Sumara, A. Wierzbicka-Miernik, W. Maziarz, M.J. Szczerba Mater. Sci. Technol. (United Kingdom). 36 (2020) 961–965.
[2] T. Graf, J. Winterlik, L. Müchler, and el., Handbook of Magnetic Materials 21, (2013) 1–75.
[3] M. Kohl, M. Gueltig, V. Pinneker, R. Yin, F. Wendler, B. Krevet, Micrs 5 (2014) 1135–1160.