Large Magnetoresistance and Magnetic Field Induced Strain in Ni42.8Co7.7Mn38.8Al10.7Heusler Alloy at Room Temperature

Single-crystalline membranes of functional materials enable the tuning of properties via extreme strain states; however, conventional routes for producing membranes require the use of sacrificial layers and chemical etchants, which can both damage the membrane and limit the ability to make them ultrathin. Here we demonstrate the epitaxial growth of the cubic Heusler compound GdPtSb on graphene-terminated Al2O3 substrates. Despite the presence of the graphene interlayer, the Heusler films have epitaxial registry to the underlying sapphire, as revealed by x-ray diffraction, reflection high energy electron diffraction, and transmission electron microscopy. The weak Van der Waals interactions of graphene enable mechanical exfoliation to yield free-standing GdPtSb membranes, which form ripples when transferred to a flexible polymer handle. Whereas unstrained GdPtSb is antiferromagnetic, measurements on rippled membranes show a spontaneous magnetic moment at room temperature, with a saturation magnetization of 5.2 bohr magneton per Gd. First-principles calculations show that the coupling to homogeneous strain is too small to induce ferromagnetism, suggesting a dominant role for strain gradients. Our membranes provide a novel platform for tuning the magnetic properties of intermetallic compounds via strain (piezomagnetism and magnetostriction) and strain gradients (flexomagnetism).

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Asymmetric magnetic-field-induced phase transformation in Fe48Mn24Ga28 Heusler alloy

Zhang

Song

et al. 2023

Applied Physics Letters

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We report on the conceptual design and experimental realization of a ternary Heusler-based ferromagnetic martensitic phase transformation alloy Fe48Mn24Ga28 that exhibits asymmetric magnetostructural coupling between the forward austenite-to-martensite and the reverse martensite-to-austenite phase transformations. By tuning the Curie temperature of the high-temperature austenite to be within the thermal hysteresis of the first-order phase transformation, dissimilar change in magnetization can be associated with the forward and reverse phase transformations, respectively. We show that such an asymmetry leads to enlargement of the thermal hysteresis with an applied external magnetic field. Furthermore, partly due to the field-enhanced thermal hysteresis, the magnetic-field-induced martensitic phase transformation is irreversible in such a system. This work suggests the intricate correlation between magnetostructural coupling, thermal hysteresis, and magnetic-field-induced phase transformation, which can be exploited for designing magnetic phase transformation alloys that show extended functionalities.

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Large Magnetoresistance and Magnetic Field Induced Strain in Ni_42.8Co_7.7Mn_38.8Al_10.7Heusler Alloy at Room Temperature

Cited by 3 publications

References 32 publications

Microstructure and properties of Ni-Co-Mn-Al magnetic shape memory alloy prepared by direct laser deposition and heat treatment

Microstructure and properties of Ni-Co-Mn-Al magnetic shape memory alloy prepared by direct laser deposition and heat treatment

Epitaxy, exfoliation, and strain-induced magnetism in rippled Heusler membranes

Asymmetric magnetic-field-induced phase transformation in Fe48Mn24Ga28 Heusler alloy

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