Berlin 2018 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 21: Poster I

MA 21.68: Poster

Dienstag, 13. März 2018, 09:30–13:00, Poster A

Large uniaxial magnetostriction with sign inversion at the first order phase transition in Mn₂GaC films — Iuliia Novoselova¹, •Ruslan Salikhov¹, Andrejs Petruhins², Arni Ingason², Johanna Rosen², Ulf Wiedwald¹, and Michael Farle^1,3 — ¹Faculty of Physics and CENIDE, University of Duisburg-Essen, Germany — ²Department of Physics, Linköping University, Linköping, Sweden — ³Center for Functionalized Magnetic Materials, Immanuel Kant Baltic Federal University, Kaliningrad, Russia

M_n+1AX_n (n = 1,2,3) phases are a family of inherently nanolaminated hexagonal compounds. The new Mn₂GaC MAX phase was synthesized as hetero-epitaxial films containing Mn as the exclusive M-element [1]. Here, we present a comprehensive study of magnetic phase transitions in the Mn₂GaC films. The Néel temperature is T_N ∼ 507 K, at T_t = 214 K the material undergoes a first order phase transition from antiferromagnetic (AFM) above T_t 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 magnetostriction coefficient across the phase transition is a consequence of the layered structure and competing AFM and FM exchange interactions between magnetic atomic layers. The sign change of the magnetostriction is accompanied by a sign change in the magnetoresistance indicating a coupling between the spin, lattice and electrical transport properties. The work is supported by DFG Grant SA 3095/2-1. [1] Dahlqvist, M. et al. Phys. Rev. B 93, 014410 (2016).