Large uniaxial magnetostriction with sign inversion at the first order phase transition in the nanolaminated Mn2GaC MAX phase

Novoselova, Iuliia P.; Petruhins, Andrejs; Wiedwald, Ulf LSF; Ingason, Arni Sigurdur; Hase, Thomas; Magnus, Fridrik; Kapaklis, Vassilios; Palisaitis, Justinas; Spasova, Marina LSF; Farle, Michael LSF; Rosen, Johanna; Salikhov, Ruslan

In 2013, a new class of inherently nanolaminated magnetic materials, the so called magnetic MAX phases, was discovered. Following predictive material stability calculations, the hexagonal Mn2GaC compound was synthesized as hetero-epitaxial films containing Mn as the exclusive M-element. Recent theoretical and experimental studies suggested a high magnetic ordering temperature and non-collinear antiferromagnetic (AFM) spin states as a result of competitive ferromagnetic and antiferromagnetic exchange interactions. In order to assess the potential for practical applications of Mn2GaC, we have studied the temperature-dependent magnetization, and the magnetoresistive, magnetostrictive as well as magnetocaloric properties of the compound. The material exhibits two magnetic phase transitions. The Néel temperature is T N  ~ 507 K, at which the system changes from a collinear AFM state to the paramagnetic state. At T t  = 214 K the material undergoes a first order magnetic phase transition from AFM at higher temperature to a non-collinear AFM spin structure. Both states show large uniaxial c-axis magnetostriction of 450 ppm. Remarkably, the magnetostriction changes sign, being compressive (negative) above T t and tensile (positive) below the T t . The sign change of the magnetostriction is accompanied by a sign change in the magnetoresistance indicating a coupling among the spin, lattice and electrical transport properties.

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Novoselova, Iuliia P. / Petruhins, Andrejs / Wiedwald, Ulf / et al: Large uniaxial magnetostriction with sign inversion at the first order phase transition in the nanolaminated Mn2GaC MAX phase. 2018.

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