Relieving the frustration through Mn${}^{3+}$ substitution in Holmium Gallium Garnet

Abstract

We present a study on the impact of Mn${}^{3+}$ substitution in the geometrically frustrated Ising garnet Ho${}_3$Ga${}_5$O${}_{12}$ using bulk magnetic measurements and low temperature powder neutron diffraction. We find that the transition temperature, $T_N$ = 5.8 K, for Ho${}_3$MnGa${}_4$O${}_{12}$ is raised by almost 20 when compared to Ho${}_3$Ga${}_5$O${}_{12}$. Powder neutron diffraction on Ho${}_3$Mn${}_x$Ga${}_{5-x}$O${}_{12}$ ($x$ = 0.5, 1) below $T_N$ shows the formation of a long range ordered ordered state with $\mathbf{k}$ = (0,0,0). Ho${}^{3+}$ spins are aligned antiferromagnetically along the six crystallographic axes with no resultant moment while the Mn${}^{3+}$ spins are oriented along the body diagonals, such that there is a net moment along [111]. The magnetic structure can be visualised as ten-membered rings of corner-sharing triangles of Ho${}^{3+}$ spins with the Mn${}^{3+}$ spins ferromagnetically coupled to each individual Ho${}^{3+}$ spin in the triangle. Substitution of Mn${}^{3+}$ completely relieves the magnetic frustration with $f={\theta }_{CW}/T_N\approx 1.1$ for Ho${}_3$MnGa${}_4$O${}_{12}$.

19 pages, 3 figures, 4 supplementary figures, accepted for publication in Physical Review B as a Rapid Communication

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