Spin-Lattice Coupling and Frustrated Magnetism in Fe-doped Hexagonal LuMnO3

Abstract

Strong spin-lattice coupling and prominent frustration effects observed in the 50\(\%\) Fe-doped frustrated hexagonal (\(h\))LuMnO\(_3\) are reported. A N\'{e}el transition at \(T_{\mathrm N} \approx\) 112~K and a possible spin re-orientation transition at \(T_{\mathrm {SR}} \approx\) 55~K are observed in the magnetization data. From neutron powder diffraction data, the nuclear structure at and below 300~K was refined in polar \(P6_3cm\) space group. While the magnetic structure of LuMnO\(_3\) belongs to the \(\Gamma_4\) (\(P6'_3c'm\)) representation, that of LuFe\(_{0.5}\)Mn\(_{0.5}\)O\(_3\) belongs to \(\Gamma_1\) (\(P6_3cm\)) which is supported by the strong intensity for the \(\mathbf{(100)}\) reflection and also judging by the presence of spin-lattice coupling. The refined atomic positions for Lu and Mn/Fe indicate significant atomic displacements at \(T_{\mathrm N}\) and \(T_{\mathrm {SR}}\) which confirms strong spin-lattice coupling. Our results complement the discovery of room temperature multiferroicity in thin films of \(h\)LuFeO\(_3\) and would give impetus to study LuFe\(_{1-x}\)Mn\(_x\)O\(_3\) systems as potential multiferroics where electric polarization is linked to giant atomic displacements.