Relieving the frustration through Mn3+ substitution in holmium gallium garnet

We present a Rapid Communication on the impact of Mn3+ substitution in the geometrically frustrated Ising garnet Ho3Ga5O12 using bulk magnetic measurements and low-temperature powder neutron diffraction. We find that the transition temperature T-N = 5.8K for Ho3MnGa4O12 is raised by a factor of almost 20 when compared to Ho3Ga5O12. Powder neutron diffraction on Ho3Mnx Ga5-xO12 ( x = 0.5,1) below T-N shows the formation of a long-range-ordered state with k = ( 0,0,0). Ho3+ spins are aligned antiferromagnetically along the six crystallographic axes with no resultant moment, whereas the Mn3+ spins are oriented along the body diagonals such that there is a net moment along [111]. The magnetic structure can be visualized as ten-membered rings of corner-sharing triangles of Ho3+ spins with the Mn3+ spins ferromagnetically coupled to each individual Ho3+ spin in the triangle. Substitution of Mn3+ completely relieves the magnetic frustration with f = theta(CW)/T-N similar to 1.1 for Ho3MnGa4O12.